APES Test 4 Unit 4 Flashcards
Part I: Plate Tectonics
Earth is divided into crustal plates that move relative to one another
Convection currents are responsible for moving the plates
Circulation of heat within earth’s interior based on density differences
Relative motion (towards, away, or along) determines features at the respective boundary
Convergent Boundaries
Two plates move toward one another’
This results in subduction zones or mountain building events
Subduction zones result in volcanoes, usually several miles away from the boundary on the overriding plate
Mountain ranges are often tall and fast growing
Convergent zones are associated with earthquakes
Divergent Boundaries
Two plates move away from one another
This usually causes volcanoes at mid ocean ridges, where new lithosphere is created.
Earthquakes are possible with magma forcing its way to the surface, but are usually not severe
Rift valleys can form if this occurs on land
Transform Boundaries
Two plates slide along one another
These plates can become stuck and build up energy, typically in fault zones
Elastic rebound described how energy is released when faults slip, much like a rubber band
Many of earth’s worst earthquakes occur along transform faults, although subduction zone earthquakes can be equally or even more devastating
Tsunamis
Large volume of water displacement from some energy input, can be earthquakes (underwater earthquakes from boundaries)
An earthquake along a subduction zone happens when the leading edge of the overriding plate breaks free and springs seaward, raising the sea floor and the water above it. This uplift starts a tsunami.
Other tsunami causes could include volcanic eruptions, NEO impacts, and even human caused
Tsunamis can only be predicted on short notice and are a serious threat to life and property
Part II: Soils
Soil is a thin layer of matter that holds nutrients, filters water, and provides a structural foundation for plants to grow in
Soil is undoubtedly important in regulating many of earth’s most important processes and maintaining ecosystem function
Soil formation, properties, horizons, and types will be discussed further
Soil Formation Factors
parent material, climate, biological, topography, time
Soil Formation Factors- Parent Material
Parent material refers to the geological component of soil- the abiotic building blocks of soil. This will be rocks and minerals
Common rocks and minerals nearby, and geological history
Effects of glaciation are a huge factor in this area (and much of the US) and influence the types of sediments found in soil- boulders, cobbles, pebbles, sand, silt, clay- which in turn, helps shape soil properties
Soil: Residual vs. Transported
Residual will form on bare rock- this may occur, for example, during primary ecological succession
Transported soil may occur when glacial till is transported to an area- a mix of sand, silt, clay in various compositions- could also form from sediment transported by streams or wind
Soil Formation Factors- Climate
Is the soil frozen for most (or all) of the year? Is it wet or dry? What kinds of organisms use it, and how do they influence it? All of this depends on the climatic zone in which the soil forms
Perhaps most important is the rate of weathering- warm soils have more chemical reactions, while temperature fluctuations help weather parent material
Large amount of precipitation can weather parent material more quickly, speeding up soil formation
Soil Formation Factors- Biological
The plants and animals that live in or use soil help influence its formation
Gophers dig holes, helping aerate the soil- large ungulates may collapse those holes
Microorganisms break down other organic matter, or fix nutrients, influencing nutrient availability- as do plants that use or fix nutrients like nitrogen
Fungi live in soil as well, and often are very important for tree health.
Soil Formation Factors- Topography
Slope- steepness- flatter areas have more well developed areas because they maintain more of their soil- while steep areas may lose it more easily to weathering processes, slowing the formation process
Aspect- direction the slope faces relative to sun- souther aspect generally has warmer temps, less moisture, as opposed to northern aspect which has wetter soils, is cooler, and usually has lusher vegetation
Soil Formation Factors- Time
All 4 of these processes occur over time, and soil develops with time
Soil formation is ridiculously slow (albeit fast on geological terms)- it takes hundreds of years for one cm of soil to form, even in warm, tropical climates with flat slopes!
Soil Horizons
O, A, B, and C are the major horizons, or layers of soil
O= organic material; decomposing leaves
A= Topsoil- minerals mixing with organic material- best growing material for plants
E= materials resistant to leaching accumulate, while nutrients move down to subsoil
B= Mineral layer of soil, usually lacking organic matter
C and R are parent material in various stages of breakdown- tree roots do not penetrate down to subsoil
Soil Triangle- Soil Classification Test
Loam is usually the best growing soil-
Soils vary considerably by biome
We will classify some soil found here according to this triangle- to do this, shake soil in a jar with water and allow it to separate into layers
STUDY SOIL TRIANGLE, REMEMBER HOW TO USE IT
