APES Unit 4 Guide: Earth's Lithosphere and Soil Dynamics

Tectonic Plates

Large pieces of the Earth's lithosphere that float on the asthenosphere.

Asthenosphere

A semi-molten layer of the mantle that flows slowly, allowing tectonic plates to move.

Convection Currents

Movements in the Earth's mantle caused by the heat from radioactive decay, which drive plate tectonics.

Divergent Boundaries

Plate boundaries where tectonic plates move away from each other, leading to seafloor spreading.

Mid-Atlantic Ridge

A notable divergent boundary that is a mid-ocean ridge in the Atlantic Ocean.

Subduction

The process where one tectonic plate is forced under another, typically at convergent boundaries.

Oceanic-Continental Convergence

A type of convergent boundary where a denser oceanic plate subducts under a lighter continental plate.

Islander Arcs

Curved chains of volcanic islands formed at oceanic-oceanic convergent boundaries.

Transform Boundaries

Plate boundaries where tectonic plates slide past each other horizontally.

San Andreas Fault

A well-known example of a transform boundary located in California.

Hot Spot

An area in the mantle where hot magma rises, causing volcanic activity in the middle of tectonic plates.

Hawaiian Islands

A chain of volcanic islands formed over a hot spot by the Pacific Plate.

Pedogenesis

The process of soil formation influenced by climate, organisms, relief, parent material, and time.

Weathering

The breakdown of rocks into smaller particles in place without movement.

Erosion

The physical removal and transportation of soil and sediment by wind, water, ice, or gravity.

Soil Horizons

Distinct layers in a soil profile, each with unique characteristics.

O Horizon

The organic layer of soil composed of decomposing leaves and organic matter.

A Horizon

Topsoil, which is a mixture of minerals and organics, most fertile layer for plants.

C Horizon

The layer of weathered rock fragments with minimal organic material.

Clay

Soil particles smaller than 0.002mm, known for high nutrient retention but poor drainage.

Loam

Ideal agricultural soil consisting of roughly 40% sand, 40% silt, and 20% clay.

Porosity

The volume of open spaces (pores) between soil particles that can hold air or water.

Permeability

The speed at which water moves through soil; high in sandy soils, low in clay soils.

Cation Exchange Capacity (CEC)

The ability of soil to hold positively charged ions (nutrients), crucial for soil fertility.

Soil Texture Triangle

A diagram used to classify soil types based on percentages of sand, silt, and clay.

Mnemonic for Soil Horizons

Only Ants Eat Bread Crumbs Regularly, representing O, A, E, B, C, R layers.