EARTH SCIENCE

 biosphere
COVERAGE: o the biosphere refers to the narrow
1. earths vital statistic and band on the Earth’s surface where
system all biological life resides.
2. layers of the Earth and its o this could range from bustling cities,
Composition lush tropical rainforests, arid deserts,
or even extreme environments like
the bottom of the ocean floor.
 Earth science
o is the study of the dynamic Earth and its  geosphere
processes, properties, structures, and its o the geosphere is the largest out of
relationship with its neighbors in space. all the spheres
o extending from the surface of the
FOUR MAIN DISCIPLINES Earth down to its center.
o it is composed of external processes
 geology that we can observe on the surface
o the study of earth materials and internal processes that happen
 meteorology deep within.
o the study of the atmosphere
LAYERS OF THE EARTH AND ITS COMPOSITION
 oceanography
o the study of oceans
 astronomy Earth can be subdivided into layers based on two
o the study of celestial bodies criteria: (1) composition (density) differences and
(2) physical properties.
EARTHS VITAL STATISTIC AND SYSTEM
BASED ON COMPOSITIONAL DIFFERENCES
the Earth is composed of systems or “spheres”,
each having their own unique properties, that  crust
continuously interact with one another o this is the thinnest and outermost
layer of the earth.
WE CAN DIVIDE THEM INTO FOUR MAJOR
SPHERES o there are two types of crust– the
continental crust and the oceanic
 atmosphere crust.
The atmosphere is a collective layer of gas
o
that envelopes the Earth  the continental crust is the older and more
- it shields the Earth and its buoyant type of crust,
inhabitants from harmful ultraviolet
(UV) radiation from the Sun; o composition consisting of granite
- maintains the warmth of the Earth’s
surface
 the oceanic crust is the younger and
- contains all of the essential gasses
denser type
needed to support life.
 hydrosphere
o it is composed of basalt
o the hydrosphere refers to the bodies of
water consisting of freely flowing bodies of
 mantle
water found on the surface of the Earth
o the mantle comprises the majority of the
o as well as water reservoirs stored below the
earth’s volume (more than 80%) and begins
ground as groundwater
where the crust ends, down to a depth of
o this sphere covers nearly 71% of the Earth’s
2,900 km.
surface.
o nearly 97.4% of the composed of saline or o the boundary between the crust and mantle
salt, the remaining 2.6% is made up of fresh is called the mohorovičić discontinuity
water,
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o at this depth, the temperature and pressure
o it can be divided into two parts: the upper conditions are high enough that rocks
mantle and the lower mantle become ductile and deform easily.
- separated by the repetti
discontinuity. - because of this, the asthenosphere
core flows more like very, very viscous
o the core begins at the mantle-core fluid (but remember: it is not liquid!)
boundary, the gutenberg discontinuity, and moves independently from the
located at the 2,900 km depth. overlying lithosphere. this is a very
important mechanism for plate
o scientific investigations led to the conclusion tectonics
that its composition is made up of a fe-ni
(iron and nickel) alloy.  mesosphere
o beneath the asthenosphere is the
mesosphere (from the greek word mesos
meaning “middle”),

o made up of the lower mantle, and reaches

down to the 2,900 km depth.

o the dominant rock type in this layer is a

silicate rock called perovskite.

o unlike the asthenosphere, the mesosphere

is much stronger and flows with more
resistance. because of the immense
pressure from the overlying layers, the
strength of this layer increases with depth.

 outer core
o unlike all the other mechanical layers, the
outer core is the only one made out of liquid
BASED ON PHYSICAL PROPERTIES — melted fe-ni alloy, to be exact.
 lithosphere o the liquid nature of this layer can be
o the lithosphere (from the greek word lithos attributed to extremely high temperatures
meaning “stone”) (more than 3000°c!) that melt fe, ni, and all
other elements.
o is a thick and brittle layer that comprises the
entire crust and uppermost layer of the o the flow of the liquid metals is responsible
upper mantle. for the earth’s magnetic field.

 asthenosphere o the outer-inner core boundary is also known

o the asthenosphere (from the greek word as the lehmann discontinuity.
asthenēs meaning “weak”)
 inner core
o is a mechanically weak layer consisting of o despite the extreme temperature, the
the lower portion of the upper mantle, overwhelming pressure in this layer forces
extending down to 660 km. the inner core to be a solid ball of mostly fe.
o it is not a “sea of molten rock”. the upper o temperatures in the inner core are similar to
mantle is actually composed of an mg- and the temperatures of the surface of the sun—
fe-rich rock called peridotite. around more than 5400°c.
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(silky), or others. brilliantly cut gems are
COVERAGE: described to have an adamantine luster
1. Minerals  crystal habit or shape.
2. Rocks o this refers to the shape of each individual
3. Depositional Environments, crystal or an aggregate of crystals
Landforms, and Waterforms o although a single mineral can occur in a
variety of shapes
o crystal habit can still be an identifying
MINERALS feature in certain minerals
 hardness.
 minerals o this refers to how resistant a mineral is to
o are building blocks of rocks. scratching. the mohs’ hardness scale is a
tool used to describe a mineral’s hardness
TO BE CONSIDERED A MINERAL, IT MUST BE relative to other minerals
THE FOLLOWING

 naturally-occurring
o man-made materials such as synthetic
diamonds cannot be considered as real
minerals
 inorganic
o organic materials such as pearls or sugar
are not minerals
 homogeneous solid
o minerals should be crystalline solids. water
is not mineral, whereas ice is considered a
mineral. mercury occurs as a liquid in its
natural state and is considered as a mineral
 has definite chemical composition
o you should be able to describe a mineral’s
composition using a chemical formula
 ordered crystalline structure
o atoms in a mineral are placed in a repetitive
and orderly manner. substances that lack
this kind of atomic structure such as
obsidian (volcanic glass) or plastic are not  cleavage or fracture
considered as minerals o cleavage refers to the tendency of a mineral
to break along preferred planes called
PROPERTIES OF MINERALS zones of weakness.
o if a mineral doesn’t break along zones of
 color weakness, a fracture is produced.
o it refers to the wavelengths of light reflected  density or specific gravity
by the minerals. while it can be tempting to o this refers to the ratio between a mineral’s
identify a mineral based on its color weight and the weight of a specific volume
o it is the least useful property because a lot of water (water has a specific gravity of 1)
of minerals can occur in different colors o heavy minerals such as gold or platinum
 luster have very high specific gravity whereas light
o it describes how light is reflected from the minerals such as graphite have low specific
mineral’s surface gravity
o a mineral could have a metallic luster or  tenacity
nonmetallic luster similar to pearls (pearly), o this describes how well a mineral handles
glass (vitreous), resin (resinous), silk stress such as breaking, crushing, bending,
or tearing.
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o minerals that are susceptible to cracking or effervescent and only show light “fizzing”
breaking are called brittle (examples: such as rhodochrosite and azurite
quartz, calcite)  odor and taste
o a mineral that deforms under stress but o you may have heard that some geologists
snaps back to its original shape after the lick rocks.
stress is removed is called elastic o while that may seem a bit wacky and weird,
(examples: mica minerals) it is true that geologists lick and even smell
o on the other hand, if a mineral is deformed rocks in order to identify them
under stress but doesn’t go back to its o halite, more popularly known as “rock salt”,
original shape, it is then called flexible is a mineral that gives off a salty taste
(example: vermiculite) o other examples are borax which gives off a
o metallic minerals such as gold, copper, or sweet taste
silver are called malleable due to their o epsomite which tastes bitter
ability to be flattened into sheets. o chalcanthite which is sweet tasting but also
o copper is also ductile because it can be slightly poisonous
drawn into thin wires without breaking. o sulfur and pyrite can be identified by their
o sectile minerals such as gold or gypsum “rotten egg”-like smell
can be carved out into thin sheets with a
knife to this date, thousands of different minerals have
 diaphaneity been identified and named– and the list grows
o this refers to how well light travels through a every year! However, only a few of these minerals
mineral are abundant on the Earth’s crust and they are
o transparent minerals allow almost all of called rock-forming minerals
the light to travel through the mineral
(examples: some quartz, some calcite)
o translucent minerals only allow some of
the light to travel and exit the mineral, giving
off a cloudy or murky appearance
(examples: smoky quartz, gypsum). opaque
minerals do not allow light to travel through
at all (examples: gold, copper, pyrite)
 magnetism
o this describes the magnetic property of a
mineral
o magnetite is an example of a strongly
magnetic (strongly attracted to magnets)
mineral. there are also moderately and
weakly magnetic minerals such as
ROCKS
chromite, ilmenite, columbite, and others.
o a lodestone is a type of magnetized
magnetite that has the ability to  igneous rocks
magnetically attract other material
o igneous rocks (from latin word ignis
 effervescence
o this describes a mineral’s reaction when meaning “fire”) are formed when molten
material cools and solidifies.
exposed to a strong acid such as hcl
(hydrochloric acid).
o when igneous rocks formed below the
o this is due to the chemical reaction that
surface of the earth, they are called
results between caco3 and hcl in carbonate
intrusive igneous rocks or plutonic
minerals and rocks
rocks. when they form on the surface, they
o highly effervescent minerals like calcite
are called extrusive igneous rocks or
exhibit intense “fizzing” or “bubbling” when
volcanic rocks.
exposed to hcl. some minerals are weakly
o intrusive and extrusive rocks
EARTH SCIENCE
- can generally be distinguished using the eroded in a process called weathering
size of their mineral grains and then buried and compacted in a
- intrusive rocks have bigger or process called diagenesis.
coarser grain crystals
o the sediments that make up sedimentary
- while extrusive rocks have smaller or rocks can come from pre-existing rocks
finer crystals. this is because higher and materials or from the remains of living
temperatures beneath the earth’s things. because of this
surface slow down the cooling rate of
minerals, giving more time for larger
crystals to form. there are two main classifications of sedimentary
rocks:
o the composition of igneous rocks largely
depends on what type of magma or lava a. clastic sedimentary rocks
they form from. the composition of magma o sediments come from pre-existing rocks.
is dependent on the amount of silica (sio2), clastic sedimentary rocks are classified
which affects its viscosity, and the based on the characteristics of their clasts
temperature. such as size, angularity/roundedness, and
sorting
- komatiite is a very rare type of extrusive
igneous rock which forms when
extremely hot lava cools rapidly and was
common during the archean eon.
however, current surface conditions do
not allow komatiite to form anymore.

- other more common types of extrusive

rocks are obsidian (formed when lava
rapidly cools; also known as volcanic
glass), bombs (rounded solidified lava
fragments), blocks (angular solidified
lava fragments), and volcanic ash.

b. non-clastic sedimentary rocks

o chemical sedimentary rocks are formed
when water evaporates, leaving behind
dissolved minerals. common examples
include halite or rock salt, rock gypsum, flint,
chert, travertine, umber, and some
limestone rocks.

 sedimentary rocks
o sedimentary rocks are formed from loose
material called sediments that have been
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o another type called biochemical or
organic sedimentary rocks are composed
of the remains of living things (shells,
bones, plant fragments, etc.). common
examples include some fossiliferous
limestone (contains fossils), chalk
DEPOSITIONAL ENVIRONMENTS
(composed of very tiny marine organisms
called coccolithophores and foraminifera),  depositional environments
coquina (composed of >2 mm shell o are the combination of chemical, physical,
fragments and grains), and coal (altered and biological aspects that dictate what type
rock from remains of plant life). of sediments, rock types, and landforms are
deposited or formed
 metamorphic rocks
o when a rock is subjected to certain  erosion
chemical (addition or removal of o is an important process in depositional
chemicals) or physical (change in environments.
temperature or pressure) processes that o it is a geological process in which earth
alter its chemical composition, materials are weathered and transported.
mineralogy, and/or texture, a erosional agents such as water, wind, ice,
metamorphic rock is formed. or animals and humans are responsible for
transporting these materials
o the original rock or “parent rock” that was o these earth materials are then “added” to an
altered is called a protolith. environment or landform in a process called
deposition
metamorphic rocks are divided into two types there are many types of depositional environments
based on their texture. but they can be classified into three main types:
o the first type is characterized by the
appearance of planar arrangement of  terrestrial environments
mineral grains called foliation or foliated o land and water forms in this type of
rocks.
environment can be found on land and
usually involve freshwater. here are some
o foliation in rock
depositional environments that fall under
- is the result of deformation and the more this category
foliated a rock, the higher the grade of
metamorphism.
fluvial rivers and streams
eolian deserts and arid
o nonfoliated rocks
environments
- usually develop in environments where
alluvial ice caps and glaciers
deformation is minimal and other factors
glacial mountainous
such as chemically-active fluids play a
environments
larger part in altering the rock. some
lacustrine lakes
common examples of nonfoliated rocks
are marble, hornfels, quartzite,
metapelite, and others.
ASSOCIATED LANDFORMS AND WATERFORMS
 rocks continually go through changes that
alter its characteristics, ultimately changing  mountains
o these are elevated (more than 2,000 ft)
 it into a different rock.
areas of land, usually results of tectonic
forces. hills are similar to mountains but with
lesser steepness (below 2,000 ft).
 plains
o these are relatively flat expanses of land
that lie above sea level. plains can occur
EARTH SCIENCE
between two mountains as a valley. a o these are areas that are near rivers or
plateau is a plain that is relatively elevated coastlines where soils are saturated or
than the surrounding land. submerged in water. swamps are wetlands
 desserts where trees dominate the plant life.
o these are areas that receive little rainfall and marshes are wetlands where moss and soft-
have high rates of evaporation. despite this, stemmed vegetation are most prominent.
the most dominant agent of erosion in these
areas is running water, followed by wind.  marine environments
 glacial environments o these are environments that can be found in
o these are areas where the most dominant the open waters, from the shallow depths to
erosional agent is ice. glaciers are large the deepest portions of the ocean.
masses of moving ice over land. ice sheets
are also large masses of ice that cover an HERE ARE EXAMPLES OF MARINE
extensive area of land (more than 50,000 ENVIRONMENTS
km2). shallow marine/reef region where sunlight
 rivers penetrates the water;
o long bodies of water that originate from high high energy
elevation (such as mountains or hills) and environment and
flow down to lower elevation (such as teeming with life
plains, mountain slopes, etc.). rivers are
usually supplied with water from rainfall, continental shelf extensions of
melted ice, or from natural springs from continental crust
underground in areas called drainage submerged by water
basins.
continental slope steep slope between
 transitional environments the shallow continental
o transitional environments represent the shelf and the deep
interface between land and sea. it is here ocean basin
where freshwater meets with seawater. deep marine region where sunlight
does not reach; low
HERE ARE SOME DEPOSITIONAL energy environment
ENVIRONMENTS THAT FALL UNDER
TRANSITIONAL ENVIRONMENTS
ASSOCIATED LANDFORMS AND WATERFORMS

beach where land meets the  oceans

sea in shallow waters o these are large bodies of water that
surround continents. seas are smaller
deltaic where the river flows bodies of saltwater enclosed or partially
into the sea; freshwater enclosed by land and are connected to the
mixes with seawater ocean.
 atolls
tidal flat : a small body of water o these are rings or partial rings of coral that
closed off from a larger usually form around a volcanic island or
body of water (the volcano that has receded or been eroded
ocean) throughout time.
 guyots
o these are elevated platforms with flat tops
ASSOCIATED LANDFORMS AND WATERFORMS formed by volcanic activity near the ocean
floor. these can be massive and reach
 deltas heights of up to more than 600 m. they are
o these are areas at the end of the mouth of a also known as seamounts.
river where freshwater mixes with seawater.
 wetlands
COVERAGE:
1. basics of stratigraphy
EARTH SCIENCE
geology. he also introduced another important
principle of stratigraphy

 principle of faunal succession.

o sedimentary strata may contain fossils of
plants and animals in a definite and
invariable sequence.
o thus, the age of a stratum and another
BASICS OF STRATIGRAPHY stratum in a different location can be
correlated if they share the same fossil
assemblage.
 stratigraphy
is a branch of geology that deals with the study of
rock layers, beds, or strata (singular: stratum) sometimes, different processes can occur that can
it is a discipline that correlates rocks and time, lead to a gap in a rock sequence called an
helping us understand how, why, and when a unconformity. the “missing time” represented by
certain configuration of strata came to be. the unconformity in a rock sequence is called a
hiatus.
in the 17th century, a catholic priest named
nicolaus steno formulated the guiding principles of THERE ARE THREE TYPES OF UNCONFORMITIES
stratigraphy:
law of superposition if the sequence is  disconformity
undisturbed, the layers o this type of unconformity is present when
on the bottom are the there is a missing stratum or strata in the
oldest while the layers sequence, usually due to a period of non-
above them are deposition or erosion.
younger.  nonconformity.
o this occurs when sedimentary strata are
law of original strata are deposited deposited on top of igneous or metamorphic
horizontality horizontally. rock bodies.
 angular unconformity.
law of lateral continuity each stratum extends o when strata are disturbed by forces that
laterally until it
cause folding, tilting, and/or faulting, they no
encounters a barrier or
longer appear horizontal. the surface is then
obstacle.
exposed to erosion and soon, another set of
sedimentary strata is deposited on top of
law of cross-cutting if a geologic body (like the disturbed sequence.
relationship an intrusion) or
discontinuity (like a
fault) cuts across
strata, then it must be
younger than the strata
it cuts.

 intrusion
o is an igneous rock body that forms when
magma cuts through sedimentary layers these principles and unconformities can be used to
and solidifies before it reaches the surface identify the age of strata in relation to other strata in
a method called relative dating. however, this
in the 19th century, an english geologist named method cannot identify the specific or absolute
william smith applied these principles and age of a stratum.
produced the first geological map of britain. since
then, he was regarded as the father of english
EARTH SCIENCE
determining the absolute age of a layer requires are the remains of life that are preserved within
certain techniques collectively known as absolute sediments and sedimentary rocks.
dating.
 paleontology
one of the best ways to date the numerical age of a is the study of fossils linking concepts of geology
rock is to use an absolute dating method called and biology in order to understand prehistoric life
radioisotopic dating or radiometric dating. over geologic time.

as you’ve learned in chemistry, isotopes are when an animal or plant dies, decomposition,
atoms of an element that have different scavengers, and other natural factors usually
numbers of neutrons and thus, different atomic remove the soft parts of the organism. so in order
masses. radioactive isotopes are unstable to produce a fossil
(parent isotopes) and lose subatomic particles or
energy over time in a process called radioactive two conditions must be observed:
decay.
(1) the organism must possess hard parts
eventually, the parent isotope’s configuration (bones, teeth, etc.) and (2) rapid burial of the
reaches a more stable configuration and turns into remains increases the chance of preservation
a daughter isotope. the half-life of a radioactive
isotope refers to the time it takes for half of the DIFFERENT WAYS A FOSSIL CAN BE
atoms in a substance to decay. PRESERVED

depending on the rock type, different radiometric  permineralization

dating methods can be used. here are some of the o this occurs when pores and open spaces in
most common radiometric dating methods: tissue (such as bone and wood) are filled up
with minerals precipitated from mineral-rich
solutions such as groundwater.
o an example of permineralization at work is
when silica precipitates inside the pores of
the wood, creating petrified wood. the image
above is an example of a permineralized
dinosaur vertebra.
 molds and cast
o when organisms buried in sediment dissolve
or decay away, it leaves behind a hollow
space called mold in the shape of the
organism. if this hollow space is eventually
filled in by minerals, a cast is made.
 amber
o organisms in amber are exceptionally
one important thing to note in the table above is preserved well, often still containing its soft
that even though 14c – 14n dating is a common parts. these organisms are preserved when
dating technique, it does not date the age of the they fall into a viscous tree sap which
sediments of the rocks. rather, it is commonly used hardens into amber.
to date fossils (which contain c) in a rock.  carbonization
o soft-bodied organisms and delicate plant
fossils are essential to stratigraphy and serve as parts can be conserved via carbonization.
a doorway through which we can know more about this happens when these organisms are
prehistoric life. buried in sediment and eventually dissolve
away, leaving behind a thin layer of carbon
FOSSILS AND GEOLOGICAL SCALE outlining the organism’s shape.
 freezing
 fossils o organisms can also be exceptionally
preserved when they are encased in ice. the
EARTH SCIENCE
image above is of lyuba, a baby mammoth flourishes and
that was found frozen in ice in Siberia diversifies (“cambrian
explosion”)
 trace fossils ordovician period : “age of
o a fossil doesn’t only pertain to the actual invertebrates”
organism. a fossil can be preserved records silurian period emergence of
of its activities such as tracks, burrows, plants on land
coprolites (fossilized poop), and gastroliths
(stomach stones). devonian period “age of fishes”;
o trace fossils can tell a lot about how an towards the end, true
organism lived– how it moved, what it ate, amphibians emerged
and other types of behavior. carboniferous period age of amphibians
mississippian amphibians
 the geologic time scale diversified; large coal
o the geologic time scale (gts) is a tool swamps formed
used by geologists in order to pennsylvanian emergence of reptiles
classify and date rocks and fossils. permian period existence of
instead of using numerical ages, time is pangaea; largest
divided into units such as eons, eras, mass extinction in
periods, epochs, and ages (in earth’s history
descending order of duration). occurred towards the
end (“the great
o the gts is maintained by an paleozoic extinction”)
international body called the triassic period dinosaurs
international commission on emerged; start of
stratigraphy (ics) which aims to create the age of
unified terminologies for geologists reptiles; first true
around the world to use in stratigraphy. mammals
(therapsids)
boundaries of time units change often, emerged as well
depending on new findings and discoveries.
jurassic period dinosaurs dominated
 based on the radiometric dating of the oldest the earth; first birds
rocks on earth, the age of earth is believed to emerged
be 4.534 billion years old. since then, a lot has cretaceous period first flowering plants
transpired on our little earth. paleogene period start of the age of
mammals
CONDENSED HISTORY OF THE EARTH neogene period mammals and birds
evolved into modern
hadean eon the formation of the forms; hominids, the
earth; magma ocean; ancestors of humans,
intense bombardment appeared towards the
of space bodies (“late end
heavy quaternary period current period; a
bombardment”) cycle of glacial and
archean eon life begins as interglacial periods
prokaryotic bacteria;
blue-green algae PLATE TECTONICS
start to produce
oxygen in the  the continental drift hypothesis
atmosphere o paved the way for the emergence and
proterozoic eon multicellular life acceptance of the plate tectonics theory.
emerges
cambrian period multicellular life
EARTH SCIENCE
o it was proposed by a german  similar fossil remains of plants and animals
meteorologist and geophysicist were found on continents that are currently
named alfred wegener. separated by large bodies of water.
o wegener hypothesized that long ago, paleontologists agreed that these organisms
there was a supercontinent that wouldn’t have been able to cross these oceans
consisted of all landmasses on earth. due to inherent characteristics
o he named this supercontinent pangaea
(from the greek words pan meaning
“all” and gaia meaning “land”).
o he and other supporters of the evidence #3. similar rock types and geologic
continental drift hypothesis collected features
evidence to substantiate their claims.

EVIDENCE OF THE CONTINENTAL DRIFT

HYPOTHESIS

evidence #1. continental jigsaw puzzle

 large mountain belts of similar ages and rock

types could be matched with each other across
continents. this is the case with the appalachian
mountains in the eastern margin of north
america being similar to the caledonian
mountains in the western margin of
scandinavia.

evidence #4. ancient climates

 if you take the boundaries of each continent and

try to fit them together, you’d get a landmass
similar to the configuration of pangaea.
 wegener argued that the remarkable fit of the
continents was more than a coincidence, citing
the almost perfect fit of south america and
africa.

evidence #2. fossils

 according to wegener, evidence suggesting that

there were glaciers before in present-day
continents (such as africa, south america, and
australia) located in the equator supported
continental drift.
 however, the opposition to the hypothesis
suggested that this may be due to a period of
extreme global cooling.
 wegener asserted that this was not the case
because there was also evidence showing that
large tropical swamps co-existed with the
glaciers at the time.
EARTH SCIENCE
2. antarctic plate
despite all these pieces of evidence, the 3. eurasian plate
continental drift hypothesis was still not 4. indo-australian plate
accepted by the scientific community mostly 5. north american plate
because of one problem: wegener could not 6. pacific plate
explain how the continents drifted. it wasn’t 7. south american plate
until after his death would the mystery be
solved. there are also minor plates such as the philippine
sea plate, juan de fuca plate, cocos plate, nazca
plate, scotia plate, and arabian plate.
The Development of the Plate Tectonics
Theory  as mentioned earlier, plates are always in
constant motion. because of this, the margins
after world war ii, extensive ocean exploration led of the plates are always interacting with one
to the discovery of the global oceanic ridge another. the sites where these margins interact
system which spans around the globe, making it are called plate boundaries.
the longest mountain range in the world (around
80,000 km long). THREE MAIN TYPES OF PLATE BOUNDARIES

 new oceanic crust forms in the axis of  divergent plate boundaries (constructive
this ridge system. margins)
 rocks become progressively older and
thicker with sediment away
 from the axis. this phenomenon was
termed as seafloor spreading by harry
hess and robert dietz.

o divergent plate boundaries are formed when

two plates move apart relative to each
other.
o these plate boundaries are also called
constructive margins because the
pulling apart of two plates results in the
migration of molten material from the
mantle to the surface, generating a new
crust. divergent boundaries can be found
both on the ocean floor and inland.
 the plate tectonics o divergent boundaries on the ocean floor
o model states that the lithosphere is broken manifest as the oceanic ridge system, which
up into rigid slabs called tectonic plates or was discussed earlier.
simply plates. these plates overlie the o new seafloor is generated via seafloor
ductile asthenosphere, allowing them to be spreading. as the seafloor gets older, it
in constant motion with respect to one gets denser and moves toward the edge
another. of the plate. simply put, younger oceanic
crust is hot and therefore less dense,
there are seven major plates that cover 94% of while the older oceanic crust is cooler
the earth’s surface area: and denser.

1. african plate
EARTH SCIENCE
- the rate of spreading varies along the  in a subduction zone, partial melting is
oceanic ridge system, going as slow as induced in the overlying continental crust,
2 cm/year or as fast as 15 cm/year. producing volcanic activity called continental
volcanic arcs. the subduction of the oceanic
o divergent boundaries that occur within a crust usually results in large, deep linear
continent generate an elongated depressions on the ocean floor called deep-
depression called a continental rift. ocean trenches.
these rifts form by the stretching and
thinning out of the lithosphere.  the deepest oceanic trench in the world is the
marianas trench in the western pacific
o the rift valleys can grow wide enough to ocean with a depth of nearly 11,000 km, deeper
split the continent apart, producing large than the height of mt. everest (8,800 km).
depressions. these depressions would
eventually be filled up with water,
producing new ocean basins.

- a good modern-day example of b. oceanic-oceanic plates convergence

continental rifting at work is the red sea
in the east african rift in eastern
africa.

 convergent boundaries (destructive

margins)

o convergent boundaries are the sites where

plates move towards each other, resulting
in a collision or one plate going under the
other in a process called subduction.
o they are called destructive margins
 when two oceanic plates collide, the older
because the crust is consumed in the
and denser one subducts.
process.
 much like oceanic-continental convergence,
a. oceanic-continental plates convergence the subduction of one plate generates
volcanism which forms a chain of volcanic
islands called a volcanic island arc or
simply an island arc.

 most of the island arcs are located in the

western portion of the pacific ocean, while
a few can be found in the atlantic ocean.

c. continental-continental plate
convergence

 in this case, the denser or heavier block

subducts or goes underneath the lesser
dense block. because the oceanic crust is
made up of basalt, it subducts underneath
the continental crust made up of the lighter
granitic material in a zone called the
subduction zone.
EARTH SCIENCE
 because continental crust is too thick and
buoyant to be subducted, the majority of the
crustal material is deformed and pushed up
instead. this results in the accumulation of
sediments and rocks along the margin, forming
mountain belts in a process called orogeny.

 the most famous example of this would be the

himalayan mountain range formed from the
collision of the indian and eurasian plates
nearly 50 million years ago.

3. transform plate boundaries (conservative

margins)

o when slippage happens, the stored energy

is released in the form of seismic waves. the
seismic waves travel through the earth and
cause it to shake.

THESE WAVES CAN BE CLASSIFIED INTO TWO

TYPES

 body waves
o body waves are waves that travel through
the interior of the earth. there are two types
 these plate boundaries are characterized by of body waves: primary waves (p waves)
two plates sliding past each other and secondary waves or (s waves).
 not destroying or producing new crustal
material. they are also called transform faults
and are usually found in fracture zones.

 fracture zones
o are linear breaks on the ocean floor that
run perpendicular to oceanic ridges. an
active transform fault lies between the two
offset oceanic ridges, while the areas
beyond the ridge zones are inactive zones.

EARTHQUAKE

 earthquakes
o occur when one block of earth slips past o primary waves
another block along surfaces called faults - these are the fastest seismic waves and
or fault planes and generates ground can travel through solid, liquid, and gas.
shaking. - these waves push and pull the rocks in
o the area under the earth where the slippage the direction the wave is traveling.
originates is called the hypocenter or - they are also called compressional
focus waves because of this behavior.
o the epicenter refers to the point on the
earth’s surface that is directly above the o secondary waves
hypocenter
EARTH SCIENCE
- these waves cause the rocks to shake thousands of earthquakes occur every day around
up and down at right angles with respect the world, but most of these are too small to be
to the direction of the traveling wave. felt by people or cause damage.
- s waves are slower than p waves and
can only travel through solids.  seismology
- because of this, s waves cannot o is the study of earthquakes.
propagate through the liquid outer core. o instruments that are very sensitive to
they are also called shear waves. ground shaking called seismographs or
seismometers are used by seismologists to
 surface waves record earthquakes.
o surfaces waves, as the name implies, can
only travel on the surface of the earth. in order to describe and classify earthquakes, the
o these are the waves that can cause intensity and magnitude are determined.
tremendous damage. there are also two
types:  intensity
refers to the qualitative measurement of the
amount of ground shaking at a certain location,
depending on the amount of damage to property,
life, and nature.

 different intensity scales are used in different

countries. in countries like the united states, the
modified mercalli intensity scale is used.

 in the philippines, however, the phivolcs

earthquake intensity scale (peis) is used. this
scale was developed by the philippine
institute of volcanology and seismology
(phivolcs) as a response to the devastating
1990 luzon earthquake.

 magnitude
 love waves o refers to the quantitative measurement of
o these waves are responsible for shaking the the amount of energy released at the
ground horizontally and vertically in an s-like earthquake’s source.
pattern. o before, the most commonly used scale for
measuring the magnitude is called the
 rayleigh waves richter scale which measures the
o these waves move in a rolling motion similar amplitude of the largest seismic wave on
to ocean waves. a seismogram.
o now, seismologists use the moment
 sometimes, before the main earthquake or magnitude (mw) scale which measures
mainshock,, smaller and weaker quakes the total amount of energy released by
called foreshocks occur, the mainshock is an earthquake. the moment magnitude
the largest quake in the sequence. scale proves to be more effective in
measuring stronger earthquakes (mw 5 and
 weaker and shorter quakes called above) than the richter scale.
aftershocks usually occur afterward. these
quakes may or may not be felt, depending on  faults
the size of the mainshock, and can even occur o where do earthquakes come from?
over a period of days, weeks, or even months. fortunately for some (and unfortunately for
others), nearly 81% of earthquakes occur
in a very tectonically-active region called
EARTH SCIENCE
the circum-pacific belt (popularly known o in a reverse fault, the hanging wall moves
as the ring of fire). up relative to the footwall.
o this type of fault is the result of
o the next most tectonically-active seismic compressional forces that push the two
belt is the alpine-himalayan belt where slabs together, shoving the hanging wall
17% of the world’s earthquakes occur. above the underlying block.
the rest of the earthquakes occur along the o these faults are also known as thrust faults,
mid-atlantic ridge in the atlantic ocean. compression faults, or reverse-slip faults.

 strike-slip faults
o in a strike-slip fault, blocks move
horizontally with respect to one another due
to shearing forces.

 left-lateral strike-slip faults (or sinistral

faults)
o occur when one block moves to the left
relative to the other block.
o right-lateral strike-slip faults (or dextral
earthquakes along the seismic belts originate
faults) occur when the block moves to the
from convergent plate boundaries. the contact
right.
between the two interacting plates is called
megathrust faults which can produce earthquakes
of mw 9.0 and above.
 oblique-slip faults
o a combination of shearing forces and
 natural or man-made events can cause
earthquakes. tensional or compressional forces would
result in an oblique-slip fault, pictured
o earthquakes caused by the eruption of above.
volcanoes are called volcanic
EARTHQUAKE RELATED HAZARDS
earthquakes.

o generally, small earthquakes called  as we all know, major earthquakes can have
devastating effects on both living and nonliving
collapse earthquakes occur when
things. depending on the destructive force of
underground caves or mines collapse.
the earthquake, it can cause the following
events:
o the detonation of explosives can also
cause earthquakes called explosion
 landslides and ground subsidence
earthquakes
o these are caused by ground shaking during
an earthquake.
 the most common type of earthquake, tectonic
earthquakes, are caused by fault movement.
o landslide
THERE ARE MAIN TYPES OF FAULTS - is a form of mass wasting where large
amounts of earth move down a slope
under the influence of gravity.
 normal faults
- they can have devastating effects
o in a normal fault, the hanging wall moves
especially in heavily populated areas
down relative to the footwall. near hillsides or mountain slopes.
o Normal faults are the result of tensional o subsidence
forces that pull the two slabs apart. - is the sudden sinking of the earth’s
o they are also known as tensional faults, surface due to the movement of the
gravity faults, or normal-slip faults. earth underneath.
o liquefaction
 reverse faults
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- is similar to subsidence but occurs facilities is also a possible threat, such as
when sediments are saturated with the leakage of radioactive water from the
water. while these events can occur fukushima nuclear power plant during the
naturally, they are usually aggravated 2011 japan earthquake.
by earthquakes.

 flooding and water-related hazards

o during and after an earthquake, large water  volcanism
pipes underground and dams may be o is a geological process where hot molten
damaged and fail. these can cause flooding rock from underneath the earth reaches the
in populated areas which may result in surface through an opening in the ground.
property damage and harm to life. the most recognizable form of an opening is
a volcano where molten material flows out
o in enclosed bodies of water such as lakes onto the surface during a volcanic eruption.
or reservoirs, waves called seiches may  eruption
occur. o describes how the molten material was
- these are oscillating waves that ejected; whether it was violent (explosive
produce major fluctuations in the eruptions), non-explosive (effusive
water level, depending on the eruptions), or what caused the eruption
strength of the earthquake. (hydrothermal, phreatic, phreatomagmatic,
etc.).
o one of the most dangerous effects of
earthquakes that originate offshore are the formation of volcanoes is deeply tied with the
tsunamis. theory of plate tectonics.

THERE ARE THREE MAIN WAYS MAGMA CAN

- tsunamis are giant waves that are RISE TO FORM VOLCANOES
produced when a fault displaces a
large slab of the ocean floor they  convergent boundaries
are nearly undetectable in the open o as previously discussed, a process called
ocean, but once tsunamis reach partial melting occurs in subduction zones,
shallow waters, wave height responsible for heating and partial melting
increases dramatically and can reach of the rocks in the overlying plate.
up to 30 m, like what happened in the
2004 indian ocean mw 9.1 o this is caused by the introduction of volatiles
megathrust earthquake in sumatra, (seawater, water from minerals, and other
indonesia. fluids) from the oceanic lithosphere, which
lowers the melting temperature of the
 damage to man-made structures surrounding rocks. the molten rock then
o depending on the material used and the starts to ascend to the surface in the form of
way they were constructed, structures such volcanic activity.
as buildings, bridges, roads, dams, and
others are susceptible to damage.  divergent boundaries
o when plates move apart, there is a
o damage can range from cracks on the reduction of pressure in the lithosphere,
walls to the total destruction of property. allowing for magma in the asthenosphere to
fires can also break out due to severed rise and induce partial melting of the
gas and electrical lines. coupled with surrounding rocks.
broken water pipelines, even small fires can
quickly spread and cause massive o a good example of divergent boundary-
damages. produced volcanism can be found in the
mid-atlantic ridge.
o spillage of hazardous chemicals from
factories and chemical containment  hotspots and mantle plumes
EARTH SCIENCE
o mantle plumes are areas where the mantle  secondary cone
rises towards the surface, originating from o smaller parasitic volcanoes that feed on the
deep within the mantle. a hotspot is the same magma chamber as the main volcano
surface manifestation of a mantle plume. through secondary vents usually emits
volcanic gas called fumaroles
o unlike the other two ways, volcanism at
hotspots does not occur at plate  pyroclastic materials
boundaries. as plates move above a o any kind of volcanic material that is
hotspot, the increase in temperature extruded by a volcano such as bombs,
induces partial melting and generates blocks, ashes, and others
hotspot volcanism.
TYPES OF VOLCANO
o the most famous example of hotspot
volcanism is the hawaiian-emperor  shield volcanoes
seamount chain. o shield volcanoes are large dome-shaped
volcanoes that have broad gentle slopes
 volcano morphology and large craters. the largest volcano on
different types of volcanoes have different shapes earth, mauna loa in hawaii, is a shield
and sizes. however, most volcanoes share certain volcano.
characteristics.
o these volcanoes get their broad form due to
the accumulation of layers of runny, fast-
moving basaltic lava flows.
HERE IS THE ANATOMY OF A GENERALIZED
VOLCANO o shield volcanic eruptions are typically
gentle and non-explosive, consisting of
lava fountains, lava flows, and rarely any
pyroclastic materials.

 cinder cones
o cinder cones (also known as scoria cones
or ash-cinder cones) are steeper and
have smaller craters than shield
volcanoes. they are usually made up of
loose pyroclastic material called scoria, a
dark-colored igneous rock that is highly
vesicular (has lots of vesicles or cavities)
made from extruded basaltic magma.
 magma chamber o cinder cone eruptions are moderately
o the reservoir of molten material in the earth explosive, with lava coming from inside the
crust; replenished with magma from a vent or at the base of the volcano. cinder
deeper reservoir in the mantle cones usually have a short lifespan and
are the most common types of
 main vent volcanoes.
o the pathway for magma to come the surface
 composite volcanoes or stratovolcanoes
 crater o a composite volcano is probably the most
o bowl-shaped depression located at the recognizable form of the volcano, with its
summit of the volcano that serves as the symmetrical steep-sided cone-shaped
opening of the volcano to the earth’s morphology. alternating layers of viscous
surface andesitic lava flows, volcanic ash, and
cinders are responsible for its shape.
EARTH SCIENCE
o eruptions tend to be violently explosive o due to extreme temperatures (from 600c to
and can cause lava flows, pyroclastic 1000 c), lava flows cannot be easily diverted
flows, large ash clouds, and even lahar. or stopped. fortunately, most lava flows can
famous examples of stratovolcanoes are be outrun by a person on foot.
mt. fuji in japan and mt. mayon in the
philippines. o there are three main types of lava flows.
- the first one is called aa flows
o when a particularly explosive eruption (pronounced as “ah-ah”) and is
occurs, the stratovolcano could collapse characterized by spiky and rough
and form a large depression called a surfaces.
caldera. our very own taal volcano is a - the second one is called pahoehoe
good example of a caldera filled in by flows (pronounced as “pa-hoy-
water, creating the taal lake. hoy”) and is described as having a
“rope-y” appearance with smooth
VOLCANO RELATED HAZARDS surfaces.
- the last one occurs when lava is
 volcanoes can be deadly forces of nature extruded along the oceanic ridge,
and impacts of volcanic hazards have been producing smooth rounded shapes
well-documented throughout the years. here are called pillow lavas.
some of the common volcanic hazards:
 volcanoes in the philippines are classified
as active (erupted within the last 600 years),
potentially active, and inactive. as of 2020,
 pyroclastic flow there are 24 active volcanoes out of 407
o a pyroclastic flow is a rapidly-moving volcanoes in the philippines (delos reyes,
current consisting of hot gases and tephra 2018).
(volcanic material) driven by gravity. they CLIMATE, WEATHER, ATMOSPHERE
are also known as nuée ardentes (french
term meaning “glowing cloud”).
pyroclastic flows usually accompany  the atmosphere is a collective layer of gas.
explosive eruptions. the air that fills our atmosphere is composed of
many different gases.

 lahars
o lahar flows occur when volcanic material
becomes saturated with water, possibly
from rainfall or melted ice, and rapidly
descends down steep volcano slopes.

o this type of volcanic hazard is particularly

dangerous because it can happen even
when a volcano is not erupting. the lahar  besides these gases, the atmosphere is also
flows during and after the 1991 mt. composed of minor and variable components
pinatubo eruption is a good example of the such as water vapor, aerosols, and ozone that
destructive power that lahar flows can bring. vary in abundance depending on time, location,
and other factors.
 lava flows
o depending on the viscosity of the lava,  despite occurring in relatively small amounts,
lava flows can spread out over large these components are still very important and
distances. runny lava flows spread out can have significant effects on the
more quickly before they solidify, compared atmosphere.
to viscous lava.
EARTH SCIENCE
 water vapor o ozone depletion became a global issue
o water vapor is the primary source of in the 20th century primarily due to the
precipitation and cloud formation in the overuse of chlorofluorocarbons (cfcs) that
atmosphere and thus, a very important entered the atmosphere and broke down
factor when predicting the weather. the ozone.

o water vapor is also one of the most

important greenhouse gases because it o this problem was addressed with the
helps absorb heat that radiates from the implementation of the montreal protocol
earth, heating the atmosphere. by the united nations in order to ban the
production and use of cfcs starting in 1987.
- greenhouse gases (ghg) are gases
that trap heat in the earth’s PARTS OF THE ATMOSPHERE
atmosphere and include other gases
such as carbon dioxide, methane,  the atmosphere is not uniform all
nitrous oxide, and ozone. humidity throughout. in
refers to the amount of water vapor fact, as you go from the bottom (earth’s surface) to
or moisture in the atmosphere. the top (towards space), you will observe changes
in temperature and pressure.
 aerosols
o these are minuscule solid and liquid  as you go up the atmosphere, the pressure
particles that are suspended in the air. decreases due to fewer air molecules
“pressing down” on you.
o common examples of aerosols are smoke,
pollen, sea salt, dust, airborne  most of the air molecules are heavy and are
microorganisms, and other natural or man- concentrated near the surface of the earth.
made sources.

o because of their size and weight, aerosols

can remain suspended in the air for long
periods of time (even years!).

o aerosols have two important functions in

the atmosphere:
- they can be “cloud seeds” or cloud
condensation nuclei upon which
clouds form and (2)
- they can also absorb, reflect, and
scatter incoming solar radiation
from the sun, preventing harsh on the other hand, temperature changes differently
amounts of uv rays that can be as you go from one atmospheric layer to another.
damaging to earth’s inhabitants.
 ozone LETS TAKE A LOOK AT THE DIFFERENT LAYERS
o as previously discussed, ozone is one of OF THE ATMOSPHERE.
the primary ghg (greenhouse gases) in
the atmosphere. it is a form of oxygen with
three oxygen atoms in each molecule (o3).

o like aerosols, ozone plays an important

part in absorbing potentially harmful uv
radiation from the sun.
EARTH SCIENCE
considered the “final frontier” of the
atmosphere.

WEATHER VERSUS CLIMATE

 as mentioned above, the troposphere is the

layer in which all weather phenomena occur.
the study of weather phenomena is called
 troposphere meteorology.
o this is the lowest layer of the atmosphere.
in this layer, temperature decreases with
increasing altitude.
o the troposphere is the most important
layer for meteorologists because all of
the weather phenomena occur here.
o the outermost boundary of the troposphere
is called tropopause.

 stratosphere
o the temperature in this region increases with
altitude because the ozone layer is
located here

o as discussed earlier, the ozone layer

becomes hot due to the absorption and
trapping of uv rays from the sun.  weather
o refers to the conditions of the atmosphere in
o commercial airplanes fly in the lower a region over a short period of time
portions of the stratosphere because of the
less frequent turbulence experienced, unlike
in the troposphere.  climate
o on the other hand, is the long-term behavior
o the end of the stratosphere is marked by of the atmosphere over a region.
stratopause.
 meteorologists use humidity, air pressure,
 mesosphere temperature, wind, and other factors in order
o the coldest temperatures in the atmosphere to gain a better understanding of weather and
(around -90°c) can be found at the end of climate in a region.
this layer at the mesopause.
 the hydrological cycle
o the mesosphere protects us from meteors water is inexplicably tied to a lot of earth processes,
by burning up most meteors and including processes in the atmosphere.
asteroids before they reach the earth’s
surface.  water goes through a constant journey of
evaporation and condensation called the
 thermosphere hydrological cycle or water cycle that is
o temperatures start to rise again in this layer primarily driven by the radiation from the sun.
regardless of what we can observe on the
due to the constant absorption of high-
earth’s surface, the hydrological cycle occurs
energy radiation from the sun by atoms of
continuously for millions of years above, on,
oxygen and nitrogen. it is in this layer where
and below the ground.
satellites orbit around the earth.
- although the water cycle does not have
a starting point, we can start in the
o at the end of the thermosphere is a very thin
layer of air called the exosphere which is
EARTH SCIENCE
ocean, where the heat from the sun condensation and form around a “cloud
evaporates water into vapor. seed” or condensation nuclei (aerosols).
soon, a cloud is formed from millions of
- these water vapors are then tiny cloud droplets.
transported into the atmosphere due
to rising air currents where they form  there are different types of clouds that are
clouds. classified according to form and height. based
on height, there are low clouds (0-2000 m),
- colder temperatures in the middle clouds (2000-6000 m), and high clouds
atmosphere encourage clouds to (over 6000 m).
condense and precipitate.
THERE ARE THREE MAIN TYPES OF CLOUDS
- precipitation reaches the surface of BASED ON THE FORM
the earth and flows down slopes as
runoff. some of the water seeps into the  cirrus clouds
ground and replenishes the groundwater o (from latin word cirrus meaning “lock of
in aquifers (underground freshwater hair”). these are thin, wispy, and white
reservoirs). clouds that resemble hair.
 stratus clouds
 eventually, all rivers and streams arrive at their o (from latin word stratum meaning “layer”).
ultimate destination, the ocean, and the cycle these are thin layers of clouds that cover
repeats. extensive portions of the sky.
 cumulus clouds
 indeed, the hydrological cycle is an o (from latin word cumulo meaning “a heap”).
important system upon which all of the these are big, cotton candy-looking clouds
earth’s residents depend on. that can stack vertically in a tower-like
manner.

WIND FORMATION

 wind
o is generated when air flows from regions of
high pressure to regions of low pressure
CLOUD FORMATION
caused by the unequal heating of the
earth’s surface.

IT IS CONTROLLED BY THE FOLLOWING

FACTORS

 pressure gradient force

o physics tells us that when an object
encounters an unbalanced force in one
direction, it will accelerate in the same
direction.
o this is what happens when there are
horizontal pressure differences in the air.
this variation in air pressure is the driving
force of the wind.
 clouds
o are one of the easily observable indicators  Coriolis effect
of weather conditions. o when the wind moves, it does not go in a
o clouds start out when water vapor in the air straight line. it is deflected from its original
changes to liquid in a process called path due to the earth’s rotation in a
phenomenon called the coriolis effect.
EARTH SCIENCE
o the earth spins in a counterclockwise o precipitation occurs when any form of water
direction and so, all free-moving objects particles descend from the atmosphere
(including the wind) are deflected to the towards the earth’s surface.
right in the northern hemisphere and to the
left in the southern hemisphere. o the most common form of precipitation is
rain (water droplets). other types of
 friction precipitation can include sleet (pellets of
o friction with the earth’s surface is caused by ice), hail (lumps of ice), snow (ice crystals),
the terrain the winds encounter. this could and drizzle (very fine water droplets).
include mountains, hills, forests, and even
man-made structures that hinder the flow of  el niño
wind. o this is a weather pattern that affects
countries near the southern pacific ocean.
OTHER TYPES OF WEATHER PHENOMENA
o during normal conditions, wind along the
 typhoons, hurricanes, and cyclones equator pushes warm surface water near
o these refer to the same thing: areas of low south america towards the western pacific
pressure that form over oceans that are countries (such as indonesia, philippines,
characterized by a spiral movement of viral etc.). the warm surface water is soon
winds. the only difference between them is replaced by cooler water from underneath.
where they formed

o typhoons are storms that form in the o however, during el niño, warm water from
western pacific. the western pacific flows instead towards
south america and up north towards the
o hurricanes are storms that form in the western portion of north america. this
atlantic ocean and eastern pacific, phenomenon induces changes in weather
patterns, marine fisheries, and ocean
o while cyclones form over the south pacific conditions.
and the indian ocean.
o el niño is part of a weather cycle called el
niño-southern oscillation (enso) and is
known as the warm phase of enso. la
niña, the cold phase, can be considered as
 thunderstorms the opposite of el niño.
o these are associated with cumulonimbus
clouds, heavy rainfall, thunder, lightning,
and sometimes tornadoes.  the philippine atmospheric, geophysical, and
astronomical services administration
o they are caused by the upward movement (pagasa) is the authority on all meteorological,
of air that is moist and warm. lightning is climatological, and astronomical phenomena
caused by the electric charge that results related to the philippines. as seen on the news,
from the collision of ice crystals (cloud pagasa
droplets) in the air. - is responsible for monitoring tropical
cyclone activity within the philippine area
 tornadoes of responsibility (par).
o these are columns of violently spinning air
that extend downwards from cumulonimbus
clouds. most tornadoes are short-lived but
can still cause extensive damage to
property, nature, and life along their path.

 precipitation
EARTH SCIENCE