Environmental Science Notes
Weathering/Erosion/Changes in the Earth Systems
New Voc. Words: mechanical and chemical weathering, frost wedging, exfoliation, hydrolysis,
oxidation, acid precipitation, erosion, deposition, mass movement erosion, creep, mudflows, landslides,
rockslides, slump, avalanches, rock falls, alluvial fan, delta, Divergent, convergent, and transform plate
boundaries, soil, soil profile, O-Horizon, A-Horizon, leaching, Ice Age, Interglacial periods , El Niño,
tributaries, trunk, divide, watershed, stream loads, suspension, bed load, young stream, stream channel,
stream bank, mature stream, meander, old stream, floodplain, Zone of aeration, cave, sinkholes, Karst
topography, spring, geyser, Travertine, stalactites, stalagmites, nutrient, territory, dormant, hibernation,
species, habitat, geographical range, population, community, ecosystem, biodiversity, transpiration,
Carbon sequestration, biomass, and prescribed burning
Earth changes occur over time due to weathering and erosion. They affect all the Earth Systems
including the Biosphere.
Weathering-Is the breaking down of rock material by mechanical or chemical means.
 Mechanical Examples:
o A tree root forcing the breakage of concrete in a cement sidewalk.
o Swift movements of a river lifting rocks from the bottom and forcing the rocks to
collide with other rocks.
o Frost wedging: The repeating thawing and freezing of water trapped in cracks of
rocks and later freezing, expanding, and breaking rocks apart.
o Exfoliation: The process of the outer layers of rock being stripped away.
What is mechanical weathering and what factors are involved?
Mechanical weathering exposes more surface area than chemical weathering and
breaks apart a rock without changing the rock mineral composition.
Factors are temperature and pressure
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Chemical Examples:
o Water is the main cause of chemical weathering because it dissolves minerals.
and then carries them away, leaving behind now a different composition.
o Hydrolysis-the reactions of water decomposing another substance.
o Water and air comes in contact with some minerals in rocks like feldspar to form
clay.
o Water and Oxygen causes oxidation (a chemical reaction occurring from the
adding of oxygen and usually water) to occur when an exposed metal such as
iron forms rust.
o Carbonic acid forms by mixing water with carbon dioxide from in the
atmosphere. This acid dissolved minerals like calcite, the main mineral in the
rock limestone. Over time this acid can dissolve enough limestone to form
underground caves.
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o Acid precipitation (usually in the form of acid rain): oxidation of sulfur dioxide to
sulfuric acid or nitrogen oxide to nitric acid. Both change the pH of rain water
from 7 to an average pH of 4.3 forming acid rain.
 Pure water has a pH of 7.0 (neutral). The normal rain pH is 5.0-5.6 due
to the natural atmospheric chemical reactions
 The formation of acid rain begins with the Sun's rays reacting to oxygen.
Then the oxygen reacts with water and sulfur dioxide or nitrogen oxide.
 Acid precipitation can be dry (smoke and dust that stick to the ground,
buildings, homes, cars, and trees) or wet (rain, fog, and snow)
 Acid rain caused problems:
 acceleration of the rusting oxidation reaction of metals
 damaging plant life including trees and forests
 lowering the pH of the soil and water
 Killing of fish and other organisms that can't adapt to the lowered
pH levels
 hastens the natural weathering process of limestone, marble, and
mortar
 the decay of paint on vehicles and buildings
 human health problems worsen (especially those with asthma)
What is chemical weathering and what factors are involved?
Chemical Weathering occurs when water, air, and other substances react with minerals in a
rock and changes the mineral's composition.
Factors are water plus some other substance
What are other factors that affect weathering?
The greater the surface area the more weathering that occurs. Sloping of topography and
decaying of organic material are also factors.
Erosion-Is the wearing away of the Earth either by surface or ground water, wind, glaciers,
and/or gravity
 Deposition is the final stage of erosion where the worn material is deposited
somewhere else.
What are the types of erosion?
1. Mass Movements-Occur when gravity alone causes loose sediments and weathered
rocks to move down a slope.
 Some are gradual while others are very quick.
 Climate has a great effect on the vegetation and the weathering that occurs in a
particular area.
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Climatic conditions determine which materials and how much of each will be
available for mass movement.
Variables:
 The material's weight
 The material's resistance to slide or flow down a slope
 A trigger is needed to shake materials loose and cause it to go down a
slope
 Water: too little water may prevent sediments from holding together
allowing movement and too much water makes a slope unstable allowing
movement
Types of Mass Movement:
a) Creep: Slowly inches down a hill (Ex. Leaning poles)
b) Mudflows: Sudden wall of mud made of mixed water and dry sediments that come
of a slope and that gets thick and pasty. (Speeds up to 100 miles/hour)
c) Landslides: A rapid, downslope movement of material that occur when a thin block
of loose soil, rock, and debris separates from the underlying bedrock.
d) Rockslides: Occurs when large blocks of rocks break loose from a steep slope (usually
after earthquakes and heavy rains).
e) Slump: Occurs when loose material or rock layers slip down a slope.
 Strong rock or sediment lies over weaker material causing the weaker to
loosen and fall
 Sometimes water penetrates the upper slopes and can't escape causing
mudslides
f) Avalanches: Landslides in mountainous areas with a large accumulation of snow.
 Three types-dry (powder is the most destructive), wet, and slab
g) Rock Falls: A rock or two falling down a slope. Common at high elevations, in steep
rock cuts, and on rocky shorelines.
2. Surface and Groundwater Erosion/Deposition-several types
a.) Alluvial fan: Fan shaped sediment pile on land (Surface water deposition)
b.) Delta: Triangular shaped sediment deposited into the mouth of an ocean, gulf, or
lake
3. Glacial Erosion
4. Wind Erosion
I. The Changing Lithosphere
 The lithosphere is the Crust and part of the Upper Mantle
o The crust is either oceanic and/or continental
 The lithosphere is made up of several movable tectonic plates that help change the
Earth.
o The movement of the plates is determined by the type of Plate Boundary
 Divergent-the plates move away from one another (often made from
continental crust)
 Rift valleys form which can later be filled with sea or ocean water
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Convergent-the plates move toward and collide into one another
 Three types
o Continental to Continental
o Continental to Oceanic
o Oceanic to Oceanic
Transform fault-the plates slide past one another in opposite directions
or at different rates or combination of both
The soil is part of the crust and changes because of natural and human disturbances.
What is soil? A mixture of weathering rock and organic matter. Soil is about 50% rock
and mineral fragments and 50% air, water, and organic matter.
What is a soil profile? The different layers of soil. Important for farmers and
gardeners to have a good top soil layer (A horizon)
What is the types of layers of soil (Horizons) in order? There are five major horizons
and then the R- horizon (non-soil layer which is the bedrock also called Regolith).
1. O Horizon-Organic layer (surface layer if present)-Composed of fresh or partially
decomposed organic material that has not been mixed into the A horizon.
 Absent in cultivated soils
 More nutrient rich than the other layers
2. A Horizon - the 1st mineral layer (top soil) has a high content of organic matter.
3. E-Horizon-is the clay, inorganic minerals, and soluble matter layer
 Contains the Zone of maximum leaching-where the process of minerals
being dissolved in water and carried down into the B-horizon.
4. B-Horizon-Below the E-horizon and contains the leaching material from the EHorizon. (Color varies due to the minerals leached-very pale brown to reddish and
yellowish color)
5. C-Horizon- contains active weathering, but it has little effect on the soil formation.
II. Changes in the Hydrosphere
 Ice age
o Glacial periods-increase in glaciers
o Interglacial periods-melting of the glaciers (occurring now)
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El Niño
o Warming of the Pacific Ocean which causes opposite conditions in some areas.
 Some drought areas get flooding
 Some areas that normally get a lot of rain have drought conditions
 Our worst snowstorms in our area often occur during these times
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Water movement
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o Erosion
o Water Cycle
o Surface Water movement
 Development of Stream Systems:
 Most streams flow downslope and later into lakes, oceans, and
tributaries (they flow into other streams increasing in size as they are
joining and adding water to it)
 Small streams are called Brooks and Creeks
 Large streams are rivers and all its tributaries
 Drainage basin/Watershed: The trunk is an area of land where a
stream gets its water.
 The trunk separates one watershed from another by high
ground called a divide (These are the branches)
 Stream loads are all the materials that the water in the stream
carries consisting of living and nonliving components.
 Materials carried are in a solution.
 Suspension: All particles small enough to be held up by the
turbulence of a stream's movement. ( sand, silt, and clay)
 Bed Load: Consist of sand, pebbles, and cobbles that the
stream's water can roll or push along the bed of a stream.
 Erosion causes the divide to make the bottom deeper than the
sides and more narrow. The steep sides are called the stream
bank.
 The largest drainage basin is the Mississippi River Drainage
Basin.
 Stages of Stream Development
1. Young Stream: (Headwaters)-fastest water
 Found in mountainous or hilly regions
 May have whitewater rapids and waterfalls
2. Mature Stream: vary in speed
 The curves in the stream are called the meander.
3. Old Stream: slowest water
 As erosion continues the stream gets very wide.
 The broad, flat valley floor carved with the curves is known as
the floodplain. Many farmers love to plant crops in their rich
fertile areas.
o Groundwater movement
 The first and shallow underground water is called the Zone of aeration. This
area allows plants to get moisture.
 A spring forms in places where the water table meets the Earth's surface.
(They are usually cold water.)
 If springs are heated to very high temperatures, the water expands
underground and forces some of it to shoot out of the ground to release the
pressure. They are known as geysers. (Old Faithful in Yellowstone National
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Park in Wyoming shoots out about 40,000 L of water and steam once each
hour.)
Groundwater will keep going lower in elevation until it reaches a layer of
impermeable rock below the aquifer. This rock acts like a barrier and the
water can't move down any deeper.
As groundwater and carbon dioxide mix they form carbonic acid and cause
erosion in cracks enlarging in the limestone forming caves.
There are three main types of caves:
1. Carbonic Acid Solution Caves- Have water pass through the air and
ground to pick up Carbon dioxide to form Carbonic Acid. Slow process.
Example: Mammoth Cave in Kentucky is the longest cave system in the
world.
2. Lava Tube Caves-Old Lava tubes that formed as the red-hot lava flows
down the side of the volcano are now empty and hollow. Example:
Hawaii Volcanoes National Park
3. Sulfuric Acid Caves-Hydrogen sulfide gas rose from petroleum deposits
deep in the ground to mix with water creating Sulfuric acid. This
substance dissolves rock much faster than Carbonic Acid leaving huge
rooms in caves. Example: Carlsbad Caverns in New Mexico
Groundwater deposits are made from natural deposits of dissolved
limestone in water with calcium ions that often drip (known as pearls) slowly
from the cracks in the cave walls and ceilings. They leave deposits of calcite.
 Travertine is the inorganic limestone that drips from caves
 Stalactites: Hang from the roof
 Stalagmites: form on the floor
Sinkholes are a depression formed when the roof of a cave collapses.
 Limestone regions with caves and sinkholes are called Karst
topography.
 Most prominent regions in the USA to have caves and sinkholes is
Mammoth Cave in Kentucky.
 Most of the lakes in Central Florida are made of sinkholes.
III. Changes in the Atmosphere
 Greenhouse effect
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Diagram from Project Learning Tree-Southeastern Forests and Climate Change
o Ozone depletion
o Interglacial climate-when glaciers are not forming
IV. Changes in the Biosphere
Organism must have food for energy in the form of nutrients to stay healthy. They must also
find water and shelter.
Competition for these items is an ongoing battle.
 Living Space
o Territory-living space claimed by an individual animal or group of animals
 Climate
o Dormant-The life processes slow down
o Hibernation-A dormant sleep-like condition
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Habitat: Where an organism lives
Geographical Range: The total area where a species lives
Population: Group of the same species living in the same geographic area
Community: All the different organism living in the same geographic range
Ecosystem: Biotic and Abiotic factors interacting together in their community
Organization (or Hierarchy) of Life
1st Organism (species)-lowest
2nd Population
3rd Community
4th Ecosystem
5th Biosphere –top
Biosphere
______________
Ecosystem
________________________
Community
____________________________________
Population
________________________________________________
Organism
You Depend on Forests For Many Things in the Environment
How does the forests benefit us?
1. Everyday needs: clean water, oxygen, nutrient cycling, carbon storage, temperature
regulation and rainfall-transpiration (the absorption and releasing of water through the roots
and leaves of trees). The movement of water can influence area temperatures and yearly
rainfall.
2. Carbon sequestration- the process through which CO2 from the atmosphere is absorbed by
plants, crops, and trees through photosynthesis, and then is stored as carbon in the biomass
(tree trunks, branches, leaves, roots, and the soil around them).
3. Heat supply: charcoal and firewood
4. Shelter: lumber
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5. Food/supplies/medicine: nuts, paper, medicine, turpentine, etc.
6. Recreation: fishing, hiking, hunting, solitude, etc.
7. Wildlife Habitat
How are forests today changing?
1. Invasive species
2. Fire-shapes many forests, allows species reproduction, influences decomposition, and
nutrient cycling
3. Forest management -prescribed burning (controls natural or man-made fires to burn in a
certain area, under specific weather conditions to reduce the fuel of a dangerous fire.
4. Climate change: The amount of CO2 in the atmosphere has increased by 35% from 1850 to
2010. Climate change has occurred mainly because of human activities: deforestation and
burning of fossil fuels. Greenhouse gases such as CO2 will warm the Earth's atmosphere,
causing changes in rainfall, sea level, and weather patterns.
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