Unit 4: Earth Systems and Resources

Notes

Tectonic plates

Lithosphere floats atop the asthenosphere and can move and break into large pieces

Plate boundaries

Convergent

Two plates pushed toward each other
One of the plates will be pushed deep into the mantle
Subduction occurs → results in uplifting plates to form large mountain chains

Divergent

Two plates moving away from each other
Causes a gap that can be filled with magma → cools to form a new crust

Transform fault

Two plates slide from side to side relative to each other

Volcanoes

Mountains formed by magma from earth’s interiors
Dormant volcanoes: not been known to erupt; it’s thought that extinct volcanoes will ever erupt again
Active volcanoes: currently erupting, have erupted within recorded history

Rift volcanoes: plates move away from each other; when it erupts, new ocean floor is formed as magma fills in where the plates have separated.
Subduction volcanoes: plates collide and slide over each other
Hot spot volcanoes: don't form at the margin of plates. Instead, they’re found over “hot spots” (areas where magma can rise to the surface through plates)

Earthquakes

Result of vibrations, often due to sudden plate movements, deep in the earth that release energy

Two plates slide past one another at a transform boundary

Focus: location at which the earthquake begins within earth
Epicenter: initial surface location of earthquake
Seismograph: measures size (magnitude) of earthquake

[1935] devised y charles richter
Richter scale measures amplitude of highest S-wave of an earthquake
Each increase in Richter number corresponds to an increase of approximately 33x the energy of the previous number

Soil

General notes

Hundreds of years old material that contains many living organisms
Around half of the volume of soil is made up of mineral materials (5% is organic matter - both living and dead)
Pores between the grains of minerals in soil are filled with air or water → so…. The size of particles that make up the soil determines the size of the pores between soil particles
Must have enough arable (suitable for plant growth) soil to meet our agricultural needs

Loamy soil is best for plant growth
Most fertile soils aggregates (clumps) because it’s bound together with organic material

Soil fertility: ability to provide essential nutrients to plants such as nitrogen (N), potassium, (K), and phosphorus (P)

Types

Clay (less than 0.002 mm in diameter)

Easily adheres to each other
There is little room between particles for water → clay soil is compact

Silt (0.002 - 0.05 mm)
Sand (more than 0.05mm)

Too large to easily stick together
Sandy soils have larger pores → hold more water

Acidity

Acidity: level of acid in substance
Alkalinity: capacity of water to resist changes in pH
pH of substance ranges from 0-14 (measure of hydrogen ion concentration)
Most soils are between 4-8 pH range

Most soils range from being neutral to slightly acidic based on pH levels

Importance of pH

Affects solubility of nutrients → determines the extent to which nutrients are available for absorption by plant roots (if it’s too acidic or too basic, certain soil nutrients can not be used by regional plants)

When the pH of soil gets more acidic, ions of heavy metals like mercury (Hg) or aluminum (Al) can leach into groundwater

Ions travel to streams and rivers→ harms both plants and aquatic life
Ex. aluminum ions can damage gills of fish and cause suffocation

Weathering

Physical/mechanical weathering:

Process that breaks rock down into smaller pieces without changing the chemistry of the rock
Typically wind and water

Chemical weathering

As a result of chemical interactions between water/other atmospheric gases and the bedrock of a region
Ex. rust → forms when iron and other metallic elements come in contact with water

Biological weathering

As a result of the activities of living organisms
Ex. tree roots growing and expanding thru rocks

Soil layers/horizons

O horizon

Uppermost horizon
Mostly made up of organic material including waste from organisms, bodies of decomposing organisms, live organisms
Dark crumbly material from the decomposition of organic material forms humus

Humus is rich in organic matter

A horizon

Made up of weathered rock and some organic material that has traveled down from the O layer
Called “topsoil”
Zone of leaching
Important role in plant growth

B horizon

Receives all minerals that are leached out of A horizon as well as organic materials that are washed down from the topsoil above
Zone of illuviation

Movement of dissolved material from higher soil layers to lower soil layers due to the downward movement of water (caused by gravity)

C horizon

Bottommost layer of soil
Composed of larger pieces of rock that have not undergone as much weathering

R horizon

“Bedrock”
Lies below all other layers of soil

Monoculture (humans)

Repeated plowing breaks down soil aggregates

Leaves “plow pan”/”hard pan” → hard, unfertile soil

Monoculture: planting of just one type of crop in a large area (modern times)

Over history, significant decrease in genetic diversity of crop species has occurred
Lack of genetic variation makes crops more susceptible to pests and diseases
Consistent planting of one crop in an area eventually leaches the soil in that area of the specific nutrients that the plant needs in order to grow

SOLUTION: crop rotation

Different crops are planted in the area in each growing season

Reliance on large machinery damages soil

Agriculture is a huge consumer of energy
Consumed energy is wasted in the production of pesticides and fertilizers and fossil fuels to run farm machinery

Industrial revolution

Huge increase in worldwide ag productivity because of the mechanization of farming
Known as the GREEN REVOLUTION → bad effects
Ex. chemical pesticides resulted in new pesticide-resistant insects → SOLUTION: genetically modified plants
Ex. increase in irrigation worldwide

Over irrigated soils undergo salinization
Soil becomes water-logged when it dries out → salt forms a layer on its surface → land degradation
SOLUTION: drip irrigation- allots an area only as much water necessary and delivers water directly to roots

Soil erosion

Small rock fragments that result from weathering might be moved to new locations thru erosion
Bare soil (no plants) is more susceptible to erosion than soil that’s covered with plants
Erosion is a continual process (constant movement of water and wind on Earth’s surface)
Bad

Removes valuable topsoil
Deposits soil in undesirable places
Eroded topsoil ends up in bodies of water

Farmers need healthy soil for planting
People rely on bodies of water that are uncontaminated with soil runoff

Causes

Logging & slash-and-burn agriculture → the removal of plants in an area makes the soil much more susceptible to agents of erosion
Over cultivation of ag fields, overgrazing, urbanization, and deforestation → incr levels of erosion

Soil conservation

Use animal waste (manure), compost, and residue of plants to increase the amount of organic matter in the soil
Practice organic agriculture

Utilize compost, manue, crop rotation, non-chemical methods to manage soil fertility and pest control
Limit or do not use chemical fertilizers, pesticides, GMOs

Modify tillage practices

Decrease breakup of soil and erosion
Ex. implement contour plowing, strip planting

Use trees and other wind barriers to reduce the force of wind

Soil laws

[1977] Soil and Water Conservation Act

Aid landowners and users
Sets up conditions to continue evaluating conditions of US soil, water, other related resources

[1985] Food Security Act (aka “Swampbuster”)

Discouraged the conversion of wetlands to non-wetlands
1990 fed legis denied federal farm supplements to those who converted wetlands to agriculture
Provided restoration of benefits to those who converted lands to wetlands

Atmosphere

General notes

Layer of gases held close to earth by force of gravity

Troposphere

10-20km (5-10 mi)
Lies closest to the earth
Where all of the weather that we experience takes place
Contains the majority of atmospheric water vapor and clouds
Gradually becomes colder with an increase in altitude (6.5℃/km)
Contains certain gases called greenhouse gases

Important: h4O and CO2
Greenhouse gases in troposphere intercept and absorb a lot of this radiation
As the sun rays strike the earth, some of the solar radiation is reflected back into space
However, GHG in the troposphere intercept and absorb this radiation

Between the troposphere is the TROPOPAUSE

Acts as a buffer between the troposphere and stratosphere
Atmospheric temperature no longer decreases with altitude; temperature increases with altitude

Stratosphere

20-50km

Sits on top of tropopause
Unlike troposphere, its gases are not very well-mixed and the temperature in the stratosphere increases as the distance from earth increases

This warming effect is because of a thin band of ozone (O3) that exists in this layer
Ozone traps the high energy radiation of the sun, holding some of the heat and protecting the troposphere and the earth's surface from this radiation

Mesosphere

50-80km
Meteors usually burn up here

Thermosphere

80-110km
Thinnest gas layer
Where auroras take place
Ionization takes place in this region

Absorbs most of the energetic charged particles such as protons and electrons (solar wind) from the sun

Reflects radio waves → makes long distance radio communication possible

Climate

General notes

Weather: day-to-day properties such as wind speed and direction, temperature, amount of sunlight, pressure, and humidity
Climate: patterns that are constant over many years (30+ years)

Avg temperature and avg precipitation amounts important to describe climate
Weather and climate of any given area is the result of the sun unequally warming the earth and the gases above it as well as the rotation of the earth

Meteorologists: scientists who study weather and climate

Air circulation

Motion of air around the globe is a result of solar heating, the rotation of earth, and physical properties of air, water, and land
Three major reasons that earth is unevenly heated

More of the sun’s rays strike the earth at the equator in each unit of surface area than strike the poles in the same unit area
The tilt of earth’s axis points regions toward or away from the sun. when pointed toward the sun those areas receive more direct or intense light than when pointed away. This causes the seasons.
Earth’s surface at the equator is moving faster than the poles. This changes the motion of air into major prevailing winds, belts of air that distribute heat and moisture unevenly. Winds moving north from the equator in the northern hemisphere are deflected to the right or east, and winds moving south from the equator in the southern hemisphere are deflected to the left or east. This deflection pattern is known as the coriolis effect.

Convection currents

solar energy warms earth’s surface → heat transferred to atmosphere by radiation heating → warmed gases expand, become less dense, and rise creating vertical currents called convection currents
Horizontal airflow: warm currents hold lots of moisture compared to surrounding air → large masses of warm moist air rise → cool air flows along earth’s surface into the area where the warm air was located → flowing air, known as horizontal airflow, is one way surface winds are created
Dew point

Warm moist air rises into the cooler atmosphere and colls to the dew point
Temperature at which water vapor condense into liquid water
Condensation creates clouds

If condensation continues and the drops get bigger, they can no longer be help up by the convection in the earth’s atmosphere and they fall as precipitation (frozen/solid)
The cold air is nor denser than the surrounding air
This air mass sinks to the earth's surface where it is warmed and gathers more moisture

Starts the convection cell rotation again

Hadley cell

Convection cell accounts for land and sea breezes, on global scale, these are hadley cells
Large hadley cell starts its cycle over the equator → warm moist air evaporates and rises into the atmosphere (precipitation in the region near the equator is one cause of abundant equatorial rainforests) → cool dry air descends about 30 degrees North and South of the equator (forming belts of deserts seen around the earth at those latitudes)

Weather events

Monsoons

Seasonal winds usually accompanied by very heavy rainfall
Cause: land heats up and cools down more quickly than water does → hot air rises from the heated land and a low pressure system is created → rising air is quickly replaced by cooler moist air that blows in from over the ocean → as this air rises, it cools → the moistures it carries is released in a steady seasonal rainfall

This process happens in reverse in the dry season → masses of air that have cooled over land blow out over the ocean

Primarily occur in coastal areas
Small scale: effect seen on shores of large lakes or bays

DAYTIME: land warms faster that does the water → air mass over land rises → air from over the lake moves in to replace it → creates breeze
NIGHT: reverse- land cools more quickly than the water → air over the lake rises → air mass from the land moves out over the lake to replace rising air → creates breeze

Rain shadow effect: air mass encounters mountain → the air will be forced to rise → air mass rises and cools → water precipitates on the ocean side of the mountain → by the time air mass reaches the opposite side of the mountain, it will basically have no moisture

Causes rapid growth of the olympic rainforest on the washington state coast (receives 5m of rain/yr; leeward side receives ~50cm rain/yr)

Tropical storms

Trade winds blow over very warm water → air warms and forms intense, isolated, low-pressure system & picks up more water vapor from the ocean surface → wind circles around the isolated low pressure air area (counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere == cornelius effect)
Low pressure system continues to move over warm water → increases in strength and wind speed

Hurricanes

Winds with speeds in excess of 130 km/hr
Rotating winds of hurricane remove water vapor from the ocean's surface → heat released as water vapor condenses
Added heat energy continues to contribute to the increase in wind speed (some have winds traveling at speeds of ~400 km/hr)

A major hurricane contains more energy than that released during a nuclear blast, but since the force is released more slowly, the damage is generally less concentrated

Called typhoons or cyclones when they occur in the pacific ocean

ENSO events

El Niño

Climate variation that takes place in the TROPICAL PACIFIC once about every 3-7 years and it lasts for about 1 year
Under NORMAL weather conditions, trade winds move the warm surface waters of the Pacific away from the west coast of Central/South America ⇒ upwelling

Cold ocean water that lies under the displaced water moves to the surface (causes thermocline to rise)
Brings nutrients with it and keeps temperature of coastal water relatively cool

DURING El Niño

Normal trade winds are weakened or reversed because of a reversal of the high and low pressure regions on either side of the TROPICAL PACIFIC

Reversal called southern oscillation

Without these regulate trade winds off the central/south american coast, upwelling slows or stops

Water off the coast becomes warmer and contains fewer nutrients
Offshore fish populations of certain coastal areas decline → bad for econ (ex. Peru relies heavily on fishing)

Northern US and Canada: warmer winters and less intense hurricane season
Eastern US; typically dry regions of Peru, Ecuador: higher than average rainfall
Philippines, Indonesia, AUS: drier than normal

La Niño

Reverse of el niño; caused by coriolis effect
Air moves toward the equator to replace rising hot air → moving air deflects to the west and helps move the surface water → allows upwelling
DURING La Niña: surface waters of ocean surrounding central/south america are colder than normal

Seasons

Caused by motion of earth around sun and Earth’s axis tilt (23.5°)
When earth is in the part of its orbit where the NORTHERN HEMISPHERE is tilted toward the sun, the northern half of the planet receives more direct sunlight for longer periods of time each day than does the southern hemisphere.
When the NORTHERN HEMISPHERE is experiencing summer, the SOUTHERN HEMISPHERE is experiencing winter
Bc of the earth’s tilt, the sun rises and sets just once a year at the NORTH and SOUTH POLES

~6 months of the year are daytime
Other ~6 months of the year are dark (nighttime)

Wind

General notes

Air that’s moving as a result of the unequal heating of the earth’s atmosphere
Part of the earth’s circulatory system; moves heat, moisture, soil, pollution around the planet
Between wind belts mentioned below, air movement is less predictable, and often no wind blows at all for days

Trade winds

Able to quickly propel trading ships across the ocean
Trade winds that blow b/t 30° latitude and the equator are steady and strong; around 11-13 mph
Types

Northeast trade winds

Northern hemisphere
Trade winds that blow from the northeast

Southeast trade winds

Southern hemisphere
Trade winds that blow from the southeast

Westerly

Northern hemisphere: travels south and west (30°-60°)
Southern hemisphere: travels north and west (30°-60°)
Ferrel cell

Movement of air that accounts for westerlies
Reverse of hadley cell
Another result of coriolis effect

Polar easterlies

Formed by similar forces as westerlies
Winds between latitudes 60° and the NORTH POLE blow from NORTH and EAST
Winds between 60° and the SOUTH POLE blow from SOUTH and EAST

Horse latitudes

Aka subtropical high
Between 30°-35° NORTH and 30°-35° SOUTH of the equator
Region of subsiding dry air and high pressure results in very weak winds
Ships relying on wind were unable to sail in these areas

Doldrums

Air near the equator is relatively still bc the air is constantly rising and not blowing
Exist between 5° NORTH and 5° SOUTH of the equator → intertropical convergence zone (ITCZ)

Trade winds converge in the region of ITCZ → produces convectional storms that produce regions with some of the world’s heaviest precipitation