ENVI SCI NOTES

Lesson 1 - Soil Erosion

Weathering vs Erosion
Weathering involves two processes [physical, chemical] that often work together
to break down rocks. Both processes occur in place. No movement is involved in
weathering.

Erosion
- the movement of weathered rocks and soil particles from one place to another.

Five Agents of Erosion

1. Water
Running water is the major cause of erosion. Water picks up and carries loose
particles of soil as it moves downhill. Water starts out in tiny grooves called RILLS.
Rills become wider and deeper called GULLIES. As gullies increase, more erosion
takes place by collapsing of the walls, and sediment can be carried far away.
Gullies turn into STREAMS which turn into RIVERS.

2. Waves
Waves carry off small rocks and sand from the beach.

3. Gravity
Erosion caused by gravity is called Mass Wasting.

Types of Mass Wasting are called Rapid Mass Wasting and Slow Mass Wasting.
1. Rapid Mass Wasting
Landslide
- the tumbling of dry soil and rocks downhill.
Mudflow
- where rain mixes with the soil to form mud which moves downhill
Slump
- a huge block of rock slides rapidly down a hillside.

2. Slow Mass Wasting

Earthflow
- a mass of soil and plant life begin to slowly move downhill after a heavy rain.
Creep
- where soil particles move slowly downhill. This is the slowest.

4. Glaciers
Glaciers
- a large mass of moving ice and snow.
Glaciers move rocks by PLUCKING where ice freezes around a rock and moves it
along as the glacier moves. Glaciers also move rocks by ABRASION where rocks
are loosened and moved by the glacier, causing scratches on the bedrock.

5. Wind
Wind moves soil by DEFLATION where wind removes loose material from the
land.
Wind barriers reduce the speed and soil carrying ability of the wind. Tree
windbreaks protect an area about ten times their height. Grass wind barriers are
more flexible and can be pushed down by high winds, reducing the protected
distance to five to seven times the barrier height.
Grassed waterways protect soil against the erosive forces of concentrated runoff
from sloping lands. By collecting and concentrating overland flow, waterways
absorb the destructive energy that would otherwise cause channel erosion and
gully formation.

Lesson 2 - Rocks and Minerals

Minerals
- the ingredients of rocks. Rocks are made up of minerals.
Mineral Properties
- used to identify minerals

Mineral Properties
1. Color
- least useful property in identifying minerals.
2. Streak
- the color of a minerals powder.
- "streak test"
3. Luster
- how the mineral surface reflects on light.
4. Hardness
- the ability of a mineral to resist being scratched.
- "scratch test"
Moh's Hardness Scale
1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond

5. Fracture/Cleavage
Fracture
- mineral breaks unevenly or irregularly.
Cleavage
- the tendency of a mineral to break evenly along its weakest plane.
6. Crystal Form
- some minerals tend to form crystals that aid in the identification of the mineral.
7. Specific Gravity
- the ratio of the density of the mineral to the density of water (1g/cm raised to 3)
8. Others
Acid Test - Calcite
Magnetic - Magnetite
Taste - Halite

A minerals properties are due to the internal arrangement of its atoms. Rocks are
classified by how they are formed.

Types of Rocks
Sedimentary Rocks:
1. Clastics
 Rocks that form when sediments (sand, silt etc.) are lithified.
Processes
 Compacting and cementing
 Vary due to grain size
2. Non-Clastics
A. Organics (bioclastics)
-form from living things.
Examples: Coal, limestone
B. Chemical (crystaline)
-formed from the evaporation or precipitation of sea water.
Examples: Halite, gypsum

Igneous Rocks
- form when liquid rocks cools and solidifies.

Intrusive
- cools below the earth's surface slowly.
Extrusive
- cools at the earth's surface quickly.

Vesicular
- gas pockets

Metamorphic Rocks
- rocks that are changed due to extreme heat and/or pressure. Metamorphic rocks
becomes harder, more dense, banded or foliated and distorted.

Regional Metamorphism
- occurs when large areas of rock are changed. Usually deep below the surface
where crustal plates collide.

Contact Metamorphism
- occurs when liquid rock comes into contact with other rocks.
Rock Cycle
Lesson 3 - Waters on Earth
Water may be available as surface water or groundwater. Water in the rivers,
lakes, and seas and in the reservoirs is considered surface water. It gets
replenished through precipitation and from runoff. The oceans of this world are
interconnected. The waters of the Atlantic, Pacific, and Indian Oceans circulate
vertically or horizontally, continuously moving although constrained by land
barriers.
Much of the rainwater that gets to the Earth’s surface evaporates back to
the atmosphere. The water that works its way below the ground through voids
and permeable rocks makes up groundwater. This seems a small amount
compared with the vast oceans. Nonetheless, it provides us with the necessary
freshwater. Groundwater flows through permeable rock materials called aquifers.
Impermeable rock materials found underground are called aquitards, as these
retard or prevent the flow of water.

Types of Bodies of Water

1. Oceans
- the oceans are vast and deep bodies of water. Usually, it is these oceans that
separate continents from one another. The oceans are bodies of salt water. 5
oceans in our world. They are the Pacific Ocean, the Atlantic Ocean, Indian Ocean,
Arctic Ocean, the Southern Ocean or Antarctic Ocean. The largest and deepest
ocean in the world is the Pacific Ocean, covering one-third of the earth’s surface.
Oceans are useful to us in many ways as they are a rich source of minerals, they
provide energy and valuable fuels like petroleum. They work as an important
channel of transportation.

2. Seas
- are also big water bodies but are definitely smaller than oceans. They are partly
enclosed by a land mass and open into the ocean. The largest of the seas is the
South China Sea which is supposed be holding hundreds of islands in its waters.
The sea, like the oceans is useful to us in many ways.It is a rich source of food
providing us with various kinds of sea food.

3. Lakes
- a water body surrounded by land on all sides. It is actually the opposite of an
island, which is a piece of land surrounded by water on all sides. Lakes can be salty
or fresh water lakes. Salty lakes are due to a lot of evaporation taking place.

4. Rivers
- are large streams that flow over the land. They are hence large flowing water
bodies, they usually end up in an ocean or sea. Rivers are fresh water bodies
which generally originate in mountainous areas or elevated areas. Rivers again are
very useful as we have seen in history, that most civilizations were formed near
the banks of the rivers, like the Egyptian Civilization on the banks of the River Nile.

5. Gulf
- is a large area of an ocean or a sea that is partially enclosed by land.

6. Bay
- is a body of water, which is again partially enclosed by land. It is a wide mouth
opening of land, where the water is surrounded by land on three sides and is
joined to the sea on the fourth side.

7. Lagoon
- a lake separated from the open sea by sand or rocks.

8. Strait
- is a narrow stretch of water which joins two larger water bodies.

9. Waterfall
- falling from a height is usually called a waterfall. A waterfall is formed when a
river flows over an edge of hard rocks and falls from a great height. Waterfalls
make beautiful tourist spots and are helpful in generating hydroelectric power.

Lesson 4 - Earth's Atmosphere

Atmosphere
- the envelope of air that surrounds the Earth where all weather events happen.

The Five Layers of the Atmosphere

1. Troposphere
- turning or change, is the layer closest to Earth’s surface so it is the lowest layer.
Weather occurs in the troposphere because this layer contains most of the water
vapor. Contains almost all of the CO2, water vapor, clouds, air pollution, weather
and life forms.

2. Stratosphere
- is the layer of air that extends to about 50 km from Earth’s surface. Many jet
aircraft fly in the stratosphere because it is very stable. It is in the stratosphere
that we find the ozone layer. The ozone layer absorbs much of the Sun’s harmful
radiation that would otherwise be dangerous to plant and animal life.

3. Mesosphere
- The layer between 50 km and 80 km above the Earth’s surface. Air in this layer is
very thin and cold. Meteors or rock fragments burn up in the mesosphere. It is the
middle layer and coldest layer. Temperatures decrease as altitude increases.

4. Thermosphere
- is between 80 km and 110 km above the Earth. Space shuttles fly in this area and
it is also where the auroras (are caused when the solar wind strikes gases in the
atmosphere above the Poles) are found. It is the upper layer. Temperatures
increase as altitude increases. It includes the Ionosphere.

5. Exosphere
- upper limit of our atmosphere. This layer of the atmosphere merges into space.
Satellites are stationed in this area, 500 km to 1000 km from Earth. Layer where
atoms and molecules “escape or exit” into space.

Exosphere: 700 to 10,000 km (440 to 6,200 miles)

Thermosphere: 80 to 700 km (50 to 440 miles)[18]
Mesosphere: 50 to 80 km (31 to 50 miles)
Stratosphere: 12 to 50 km (7 to 31 miles)
Troposphere: 0 to 12 km (0 to 7 miles