EARTH SCIENCE

EARTH’S SYSTEM
The spheres are the four subsystems that make up the planet Earth. They are called spheres because they are round, just like the Earth. The four
spheres are the geosphere/lithosphere (all the rock on Earth), hydrosphere (all the water on Earth), atmosphere (all the gases surrounding Earth), and
biosphere (all the living things on Earth).

1. Lithosphere

The solid earth sometimes called the geosphere, has a layered structure in a spherical-shell form. These layers can be defined by their chemical or
physical properties, including their rock minerals. It starts at the ground and extends all the way down to Earth’s core. We rely on the geosphere to
provide natural resources and a place to grow food. Volcanoes, mountain ranges, and deserts are all part of the geosphere.

2. Biosphere

The biosphere is composed of all living organisms: plants, animals and one-celled organisms alike. Most of the planet's terrestrial life is found in a
zone that stretches from 3 meters below ground to 30 meters above it. In the oceans and seas, most aquatic life inhabits a zone that stretches from the
surface to about 200 meters below. The living portion of the Earth interacts with all the other spheres. Living things need water (hydrosphere),
chemicals from the atmosphere, and nutrients gained by eating things in the biosphere.

3. Hydrosphere

The hydrosphere is composed of all of the water on or near the planet's surface. This includes oceans, rivers, and lakes, as well as underground
aquifers and the moisture in the atmosphere. Scientists estimate the total amount at about 1.3 billion cubic kilometers. It includes the oceans, rivers,
lakes, groundwater, and water frozen in glaciers. 97% of water on Earth is found in the oceans. Water is one of the most important substances needed
for life and makes up about 90% of living things. Without water, life would not be possible.

4. Atmosphere

The atmosphere is the body of gasses that surrounds our planet, held in place by earth's gravity. Most of our atmosphere is located close to the earth's
surface where it is most dense. The air of our planet is 79% nitrogen and just under 21% oxygen; the small amount remaining is composed of argon,
carbon dioxide, and other trace gases. It consists of five layers and is responsible for Earth’s weather. Even though it seems like air is made of
nothing, it consists of particles too small to be seen. All these particles have weight that push down on Earth. The weight of air above us is called air
pressure.

ROCKS AND MINERALS

A mineral is a naturally occurring substance with distinctive chemical and physical properties, composition and atomic structure. Rocks are generally
made up of two of more minerals, mixed up through geological processes.

Minerals make up rocks. Rocks are formed in many environments upon and within the Earth's crust. There are three types of rock, each formed in a
different way. Igneous rock, formed by the cooling of magma (molten rock) inside the Earth or on the surface. Sedimentary rocks, formed from the
products of weathering by cementation or precipitation on the Earth’s surface. Metamorphic rocks, formed by temperature and pressure changes
inside the Earth. All three types of rock make up the Earth’s lithosphere, the outermost layer.

INTERNAL PROCESSES

Both volcanoes and earthquakes occur due to movement of the Earth’s tectonic plates. They are both caused by the heat and energy releasing from
the Earth’s core. Earthquakes can trigger volcanic eruptions through severe movement of tectonic plates.

Earthquake Focus and Epicenter

Movement along a fault releases strain energy. Strain energy is potential energy that builds up in rock when it is bent. When this potential energy is
released, it moves outward from the fault in the form of seismic waves. The point inside Earth where this movement first occurs and energy is
released is called the focus of an earthquake. The point on Earth’s surface located directly above the earthquake focus is called the epicenter of the
earthquake.

Seismic Waves

After they are produced at the focus, seismic waves travel away from the focus in all directions. Some seismic waves travel throughout Earth’s
interior, and others travel along Earth’s surface. The surface waves cause the most damage during an earthquake event.

Primary waves, also known as P-waves, travel the fastest through rock material by causing particles in the rock to move back and forth, or vibrate, in
the same direction as the waves are moving.

Secondary waves, known as S-waves, move through rock material by causing particles in the rock to vibrate at right angles to the direction in which
the waves are moving. P- and Swaves travel through Earth’s interior. Studying them has revealed much information about Earth’s interior.
Surface waves are the slowest and largest of the seismic waves, and they cause most of the destruction during an earthquake. The movements of
surface waves are complex. Some surface waves move along Earth’s surface in a manner that moves rock and soil in a backward rolling motion.
They have been observed moving across the land like waves of water. Some surface waves vibrate in a side-to-side, or swaying, motion parallel to
Earth’s surface. This motion can be particularly devastating to human-built structures.

EXTERNAL PROCESSES

 Weathering is any reaction, either physical or chemical, that occurs at the interface between a rock’s surface and the atmosphere such that
the rock disintegrates or decomposes.
 Mass wasting is the transfer of rock and soil downslope under the influence of gravity.

Mass wasting is a rapid form of erosion that works primarily under the influence of gravity in combination with other erosional agents.

Can result in small or large scale changes to the landscape depending on the type of event.

Rock Falls /Landslides/Debris / Mud Flows /Slumps /Creep

 Erosion is – the physical removal of material by mobile agents such as water, wind, ice, or gravity.
Water erodes rocks and the landscapes by transporting weathered materials from their source to another location where they are deposited.
Wind erodes materials by picking them up and temporarily transporting them from their source to another location where they are
deposited.
o fluvial erosion (water) • aeolian (wind) erosion • rocks falls or landslides (mass-wasting) erosion

Ice erosion occurs when particles are plucked up or incorporated by moving ice, such as a glaciers, and are transported downhill.

Gravity facilitates the down slope transportation of loosened, weathered materials and enables them to move without the aid of water, wind, or ice.
Gravity related erosion is a major component of mass-wasting events.

 Deposition is the process by which weathered and eroded materials are laid down or placed in a location that is different from their source.

GLACIERS

A glacier is a large accumulation of ice and snow that slowly moves over land. At higher elevations, more snow typically falls than melts, adding to
its mass. Eventually, the surplus of built-up ice begins to flow downhill. At lower elevations, there is usually a higher rate of melt or icebergs break
off that removes ice mass.

There are two main categories of glaciers: alpine glaciers and ice sheets (and ice caps and icefields, which are like small ice sheets). Alpine glaciers
are frozen rivers of ice, slowly flowing under their own weight down mountainsides and into valleys. Unlike alpine glaciers, ice sheets, like on
Greenland and Antarctica, and ice caps, like in Iceland, are unrestricted; they spread out in broad domes in multiple directions.

An ice sheet is a mass of glacial ice that sits on land and extends more than 50,000 square kilometers (19,300 square miles). Ice sheets once covered
much of the Northern Hemisphere during a series of Pleistocene Ice Ages. Now, Earth has just two ice sheets, one covers most of Greenland, the
largest island in the world, and the other spans across the Antarctic continent. Ice sheets are constantly in motion, spreading out in broad domes.

Ice caps are miniature ice sheets. An ice cap covers less than 50,000 square kilometers (19,300 square miles) and comprises several merged glaciers.
Like ice sheets, ice caps tend to spread out in dome-like shapes as opposed to occupying a single valley or set of connected valleys.

Icebergs are large floating chunks of ice, detached from a glacier, such as an alpine glacier or ice sheet, and carried out to the ocean. The word
iceberg literally means ice mountain, berg borrowed from German.

How do glaciers form?

Glaciers begin to form when snow remains in the same area year round, where enough snow accumulates to transform into ice. Each year, new layers
of snow bury and compress the previous layers. This compression forces the snow to recrystallize, initially forming grains similar to the size and
shape of sugar grains.

Gradually, the grains grow larger and the air pockets between the grains get smaller, causing the snow to slowly compact and increase in density.
After about a year, the snow turns into firn—an intermediate state between snow and glacier ice. At this point, it is about two-thirds as dense as
water. Over time, larger ice crystals become so compressed that any air pockets between them are very tiny. In very old glacier ice, crystals can reach
the size of an adult fist. For most glaciers, this process takes more than a hundred years.

HYDROSPHERE

A hydrosphere is the total amount of water on a planet. The hydrosphere includes water that is on the surface of the planet, underground, and in the
air. A planet's hydrosphere can be liquid, vapor, or ice.

The hydrologic cycle describes the continuous interchange of water among the oceans, atmosphere, and continents. Powered by energy from the sun,
it is a global system in which the atmosphere provides the link between the oceans and continents. The processes involved in the water cycle include
precipitation, evaporation, infiltration (the movement of water into rocks or soil through cracks and pore spaces), runoff (water that flows over the
land, rather than infiltrating into the ground), and transpiration (the release of water vapor to the atmosphere by plants). Running water is the single
most important agent sculpturing Earth’s land surface.

The two main factors between groundwater and surface water are where the sources originate from and the difference in water quality. Groundwater
comes from beneath the Earth's surface, whereas surface water is found on top of the Earth's crust in lakes, rivers, and so on.

ATMOSPHERE

Earth’s atmosphere has five major and several secondary layers. From lowest to highest, the major layers are the troposphere, stratosphere,
mesosphere, thermosphere and exosphere.

Troposphere. Earth’s troposphere extends from Earth’s surface to, on average, about 12 kilometers (7.5 miles) in height, with its height lower at
Earth’s poles and higher at the equator. Yet this very shallow layer is tasked with holding all the air plants need for photosynthesis and animals need
to breathe, and also contains about 99 percent of all water vapor and aerosols (minute solid or liquid particles suspended in the atmosphere). In the
troposphere, temperatures typically go down the higher you go, since most of the heat found in the troposphere is generated by the transfer of energy
from Earth’s surface. The troposphere is the densest atmospheric layer, compressed by the weight of the rest of the atmosphere above it. Most of
Earth’s weather happens here, and almost all clouds that are generated by weather are found here, with the exception of cumulonimbus thunder
clouds, whose tops can rise into the lowest parts of the neighboring stratosphere. Most aviation takes place here, including in the transition region
between the troposphere and the stratosphere.

Stratosphere. Located between approximately 12 and 50 kilometers (7.5 and 31 miles) above Earth’s surface, the stratosphere is perhaps best known
as home to Earth’s ozone layer, which protects us from the Sun’s harmful ultraviolet radiation. Because of that UV radiation, the higher up you go
into the stratosphere, the warmer temperatures become. The stratosphere is nearly cloud- and weather-free, but polar stratospheric clouds are
sometimes present in its lowest, coldest altitudes. It’s also the highest part of the atmosphere that jet planes can reach.

Mesosphere. Located between about 50 and 80 kilometers (31 and 50 miles) above Earth’s surface, the mesosphere gets progressively colder with
altitude. In fact, the top of this layer is the coldest place found within the Earth system, with an average temperature of about minus 85 degrees
Celsius (minus 120 degrees Fahrenheit). The very scarce water vapor present at the top of the mesosphere forms noctilucent clouds, the highest
clouds in Earth’s atmosphere, which can be seen by the naked eye under certain conditions and at certain times of day. Most meteors burn up in this
atmospheric layer. Sounding rockets and rocket-powered aircraft can reach the mesosphere.

Thermosphere. Located between about 80 and 700 kilometers (50 and 440 miles) above Earth’s surface is the thermosphere, whose lowest part
contains the ionosphere. In this layer, temperatures increase with altitude due to the very low density of molecules found here. It is both cloud- and
water vapor-free. The aurora borealis and aurora australis are sometimes seen here. The International Space Station orbits in the thermosphere.

Exosphere. Located between about 700 and 10,000 kilometers (440 and 6,200 miles) above Earth’s surface, the exosphere is the highest layer of
Earth’s atmosphere and, at its top, merges with the solar wind. Molecules found here are of extremely low density, so this layer doesn’t behave like a
gas, and particles here escape into space. While there’s no weather at all in the exosphere, the aurora borealis and aurora australis are sometimes seen
in its lowest part. Most Earth satellites orbit in the exosphere.

The Edge of Outer Space. While there’s really no clear boundary between where Earth’s atmosphere ends and outer space begins, most scientists use
a delineation known as the Karman line, located 100 kilometers (62 miles) above Earth’s surface, to denote the transition point, since 99.99997
percent of Earth’s atmosphere lies beneath this point. A February 2019 study using data from the NASA/European Space Agency Solar and
Heliospheric Observatory (SOHO) spacecraft suggests, however, that the farthest reaches of Earth’s atmosphere — a cloud of hydrogen atoms called
the geocorona — may actually extend nearly 391,000 miles (629,300 kilometers) into space, far beyond the orbit of the Moon.

IMPORTANCE OF ATMOSPHERE

Earth’s atmosphere isn’t something we can take for granted. Without it, life as we know it wouldn’t exist. Not only does it contain the oxygen we
need to live, but it also protects us from harmful ultraviolet solar radiation. It creates the pressure without which liquid water couldn’t exist on our
planet’s surface. And it warms our planet and keeps temperatures habitable for our living Earth.

In fact, Earth’s atmosphere is very thin, with a mass only about one-millionth that of the planet itself. Further, about 80 percent of the atmosphere is
contained within its lowest layer, the troposphere, which is, on average, just 12 kilometers (7.5 miles) thick.

ASTRONOMY

Astronomy is the study of everything in the universe beyond Earth’s atmosphere. That includes objects we can see with our naked eyes, like the Sun ,
the Moon , the planets, and the stars . It also includes objects we can only see with telescopes or other instruments, like faraway galaxies and tiny
particles. And it even includes questions about things we can't see at all, like dark matter and dark energy .

ASTRONOMY VS. ASTROLOGY

Astronomy is the study of the universe and its contents outside of Earth's atmosphere. Astronomers examine the positions, motions, and properties of
celestial objects. Astrology attempts to study how those positions, motions, and properties affect people and events on Earth.

What are the 4 types of astronomy?

ASTROPHYSICS: Applying the laws of physics in space.

ASTROGEOLOGY: Examining rocks, terrain, and material in space.

ASTROBIOLOGY: Searching for life outside Earth.