Unit 4– Earth Systems and Resources
Module 19– Plate tectonics
Earth is comprised of layers from the core to the tectonic plates on the surface
When earth was just molten rock, the elements separated according to their mass— with heavier elements sinking toward the center
Layers
Core: the innermost interior, comprised of iron and nickel (with a liquid outer layer and solid inner layer)
Mantle: the layer above the core containing magma, the asthenosphere, and the solid upper mantle
Asthenosphere: the outer part of the mantle, composed of semi-molten rock
Lithosphere: the outermost layer of the earth, including the solid upper mantle and crust
Tectonic plate movement creates major geographic features on earth
The theory of plate tectonics: all continents were joined in a single landmass— Pangea— and have moved over time
Earthquakes and volcanoes
Earthquakes form as potential energy is released from the movement of tectonic plates
Measured by the Richter scale, which increases with a factor of 10
Volcanoes form as the hot liquid center of the earth is because of the radioactive decay of various isotopes, which cause magma to well upward and produce hotspots where mantle reaches the lithosphere
Heat from the rising mantle plume melts at the crust, forming a volcano which is a vent that emits ash, gases, and lava- forming islands over time (like Hawaii)
Earthquakes and volcanic activity can cause tsunamis, where a series of waves in the ocean caused by seismic activity results in a massive displacement of water
Boundaries
Divergent: an area below the ocean where tectonic plates move away from each other
Seafloor spreading: caused by a divergent boundary, where rising magma forms new oceanic crust on the seafloor at the boundaries between plates
Convergent boundaries: one plate moves toward another plate and collides
Subduction: the edge of an oceanic plate moves under a continental plate because an oceanic plate is more dense, and is pushed to the center of the earth
Island arc: a chain of islands formed as a result of subduction
Collision zone: two continental plates are pushed together and form a mountain range
Transform boundary: an area where tectonic plates move past each other
Creates faults: fractures in rock caused by movements of the earth’s crust
Consequences of plate movement on biodiversity: allopatric Speciation
Plate boundaries determine the location of many volcanoes, island arcs, earthquakes, hotspots, and faults
Environmental and human impacts: can damage businesses, people, and ruin populations (like in Haiti)— which has evolved in people creating earthquake resistant buildings
Volcanoes can be bad for lungs, etc
Module 20– Soil formation, erosion, composition, and its properties
The three major types of rock are formed by different combinations of heat and pressure
Igneous rocks (basalt, granite): formed directly from magma
Sedimentary rocks (limestone, conglomerate): formed when sediments like muds, sands, or gravels is compressed by overlying sediments
Metamorphic rock (marble, slate): forms when sedimentary rock is subjected to high temperature and pressure
Rock cycle: rock is weathered to form sedimentary rock, melted tom form igneous cook, and slightly melted to form metamorphic rock
Rock is broken down by weathering and erosion
Weathering:
Physical weathering is when water, wind, freeze-thaw cycles, etc. cause the mechanical breakdown of rocks
Chemical weathering is when rocks and minerals are dissolved by chemical reactions
Acid rain can weather away rock
Erosion the physical movement of rock fragments from a landscape or ecosystem
Poor human land processes can lead to erosion
Streams, glaciers, etc. continue to grind and carve rock surface
Soil forms as a result of parent material, climate, topography, organisms, and time
Soil is good b/c it allows plants to grow, breaks down organic material, filters after, and is a habitat for many organisms
Parent material is the underlying rock material, which is weathered and fragments move upward
Climate affects soil formation because colder climates slow decomposition, whereas hotter climates accelerate soil formation because of more rapid weathering, leaching, and decomposition
Topography: soil that forms on steeper areas is more subjected to erosion and landslides
Organisms: some that burrow mix the soil, whereas others recycle organic matter
Time: more time untouched results in more fertile soil, soils with more water or soils that have been farmed tend to be less fertile
Soil horizons: layers
O horizons the organic horizons, which is composed of organic detritus
Humus: the most fully decomposed organic matter
O (Organic), A (topsoil), E (leaching occurs), B (subsoil), C (subsoil— least weathered, most close to parent material)
Soil erodes by wind and water, as well as increases in human activities
Erosion by water: when plant roots are removed, water can remove large amounts of soil
Erosion by wind: with nothing holding soil together, wind can remove the top layers and fertility is reduced— can result in dust storms
Soils have different physical, chemical, and biological properties that affect productivity
Physical properties:
Porosity: size of air spaces between particles
Composition: ratios of sand, silt, and clay
Water holding capacity: how much water soil can hold (The smaller the particle, the more it holds on to water)
Permeability: the ability of water to move through soil (the smaller the particle, the less it drains)
Chemical properties:
Cation exchange capacity: (cations= mineral ions that are absorbed by clay which has a negative charge and are used by plants as nutrients)—> is a soil’s nutrient holding capacity
Base saturation: proportion of soil bases to acids
Biological properties:
Organisms like fungi, worms, bacteria, moles, Protozoa
Module 21– Watersheds
Watershed: all the land in an area that drains into a particular stream, river, lake, or wetland
Watersheds are characterized by their area, length, slope, soils, and vegetation
Area and length: some can be small, some are huge— like the Mississippi watershed
Greater watershed length means water has to travel longer to drain
Slope: the steepness of the land
Smaller slopes means gradual flow, which results in little erosion and collects little sediment
Higher slopes result in faster drainage which allows for more displacement of rocks and things like erosion
Soil type: more permeable soil means less remains to drain, and smaller particles means water can collect these particles into water bodies (which can prevent things like light penetration for producers)
Vegetation type: plants with longer root systems can better hold on to soil and prevent sediment erosion, playing a role in the amount of sediments taken away
Humans impact watersheds by altering water flow and inputting excess nutrienst and soil
The Hubbard Brook watersheds: case study where scientists cut down all the vegetation and measured concentrations of nitrate in water, where the nitrate increased (showing trees take up nitrate and filter water)
Chesapeake bay watershed: massive watershed/ estuary that provides many services like moving contaminants—> where excess nutrients that come from the runoff of fertilized fields leads to algal blooms and dead zones in the bay
Leading people to develop the Chesapeake bay actin plan to address the reduction of the impact of nutrients
Module 22– Earth’s atmosphere, global wind patterns, solar radiation, and earth’s seasons
Insolation: incoming solar radiation
Solar radiation varies due to Earth’s curvature and tilted axis
Effects of latitude: higher latitudes means sunlight must pass through more atmosphere, losing more energy than to the tropics
Uneven heating is caused by the angle at which the sun rays strike the earth, the variation in surface area over which the sun’s rays are distributed, and some areas reflecting more energy than others (reflection= albedo)
Effects of seasons: Uneven heating can also result in earth’s tilt from the sun
The atmosphere is dominated by nitrogen and oxygen gases
Mainly nitrogen
The layers of the atmosphere differ in mass, pressure, and temperature
Layers (closest to surface- farthest):
Trophosphere: most nitrogen, oxygen, and water vapor also where weather occurs
Stratosphere: less dense, where ozone has a layer
Mesosphere, thermosphere (blocks radiation), and exosphere (where satellites are): pressure and density decreases as we go up
Air circulates in the atmosphere as a result of changing density, water vapor capacity, and temperature
Saturation point: maximum amount of water vapor in the air at a given temperature
Adiabatic cooling: rising air has less pressure, which allows the air to expand in volume— leading to a decrease in temperature
Adiabatic heating: When air sinks toward the surface, the pressure increases— which means the volume decreases and this raises the temperature
Latent heat release: the release of energy when water vapor in the atmosphere condenses into water
Atmospheric convection currents are driven by solar radiation at the equator
Atmospheric conversion currents: patterns of air movement initiated by unequal heating of earth
The warming of humid earth at the surface leads to a decrease in density, causing the air to rise, leading it to experience adiabatic cooling— leading air to reach its saturation point that leads to precipitation. The air sinks back, and is then warmed again
Hadley cells: a convection currents in the atmosphere that cycles between the equator at 30 degrees north and 30 degrees south
Solar energy warms humid air, and the air contains little vapor after cooled— leading to the formation of deserts
Intertropical convergence zone: the latitude that receives the most intense sunlight
Polar cells: convection currents in the atmosphere, where air rises at 60 degrees north and south, and sinks at 90 degrees north and south
Ferrel cells: lie between Hadley and polar cells, allowing for a wide range of currents
Earth’s rotation causes the Coriolis effect, which deflects global wind patterns
Coriolis effect: the deflection of an object’s path because of the rotation of the earth
Impacts different wind patterns, creating things like westerlies where wind movement toward the poles is deflected to the east, and prevailing winds come from the southwest and northwest as a result
Easterlies are formed when polar cells’ movements are deflected west and therefore come out of the northeast
Module 23: Earth’s geography and climate: El Niño and La Niña
Ocean currents are driven by unequal heating, gravity, wind, salinity, and the location of continents
Unequal heating and gravity: warm water rises and expands, which makes water flow away from the equator because of gravity
Wind and the Coriolis effect: trade winds push water from the northeast to the southwest in the northern hemisphere, and the Coriolis effect deflects this current so water moves from east to west at the equator
Reveals a pattern: ocean surface currents rotate clockwise in the northern hemisphere, and counterclockwise in the southern (aka a gyre)
Upwelling: surface currents separate, causing deeper water to rise and replace water moved away— or upwelling— which brings nutrients from the ocean bottom that supports producers, which support fish
Deep ocean currents: thermohaline circulation (drives the mixing of surface water and deep water because surface level with salt freezes and then moves to a place where it cools, causing remaining water to have a higher salt concentration leading it to become more dense and sink and mix with deep ocean water)
Rain shadows cause mountains to be dry on one side
Precipitation falls on a mountains’ windward side, where the cold dry air moves to the leeward side where it experiences Adiabatic heating and produces arid conditions on the leeward side
Also called a rain shadow
The El Niño southern oscillation is caused by a shift in prevailing winds and ocean currents that alters global weather
ENSO: phenomenon where trade winds weaken or reverse in direction, allowing warm water to move toward South America suppressing upwelling off the coast of Peru
Can decrease fish populations b/c no upwelling
Impacts crop production and leads to food shortages
Reversal is called La Niña: where winds reverse strongly, causing regions that were hot and dry to come back cooler and wetter