Sedimentary Rocks and WES Test Study Guide

Rock Cycle

the process by which all rocks are formed and how earth materials are recycled over time (there is no beginning or end to the rock cycle)

Rock Formation

Igneous, Sedimentary, Metamorphic

Igneous

cooling and hardening (recrystallization) of magma or lava

Sedimentary

weathering and erosion makes sediments which are then compacted and cemented into rock

Metamorphic

heat and pressure

Sedimentary Rocks

most common type of rock; makes up 75% of Earth’s surface

How are sedimentary rocks formed?

broken down (weathering), carried away (erosion) by wind, water, ice, or gravity, then compacted or cemented together

What are sediments?

bits of rocks that have been broken down at the surface (weathering)

What do sediments form?

sediments form the pieces of clastic sedimentary rocks

What are examples of sediments?

clay, sand, gravel

Weathering

the process by which rocks are broken down chemically and physically by the action of water, air, and organisms

Erosion

transportation of earth materials by water, wind, ice, or gravity

Deposition

process of where sediments are laid down onto land

Compaction/cementation

“glues” the sediments together to form a rock

Formation example

granite to sand to sandstone

How are sedimentary rocks classified?

formation (how the rock was formed)

Clastic (clast - rock)

sedimentary rock made up of sediments or pieces of other rocks; EX: conglomerate (pebbles)

Chemical (non-clastic)

sedimentary rock formed by evaporation or precipitation; EX: limestone, rock salt, flint

Biological/Biochemical (organic)

sedimentary rocks formed from the remains of living plants or organisms and may contain fossils; EX: fossiliferous, limestone, bituminous coal, coquina

What are features of sedimentary rocks?

rocks deposited in horizontal layers; features: fossils, ripple marks, mud cracks

Physical/Mechanical weathering

weathering that breaks down rocks without changing their chemical composition

What are examples of physical/mechanical weathering?

Exfoliation: removing the thin, upper layer; Frost Wedging: rock expansion caused by the freeze/thaw cycle; Abrasion: scraping/grinding action

Chemical weathering

minerals within rocks at the surface are broken down; composition IS changed

What are examples of chemical weathering?

Hydrolysis: change of a rock using water (hydro-water; lysis-break down); feldspar turns clay in water; Oxidation: change in a rock using oxygen; hematite turns red because of iron exposed; Carbonation: change in rock using carbonic acid formed from CO2 dissolving in water

What mineral is the most common to resist weathering?

Quartz

In warm, wet areas, the rate of chemical weather is ____

high

In areas subject to the freeze/thaw cycle or river action, physical weathering is ____

high

Wind erosion

abrasion, sand dunes

Weathering is ____ ______ in deserts due to ____ __ _____

greatly reduced; lack of water

Erosion is _______ due to wind action

abundant

Water erosion

abrasion, carrying capacity is high in faster moving water

Ice erosion

abrasion, carries large, unsorted loads

What is a glacier?

thick sheet of ice

Valley glacier

forms on the tops of mountains (Alps)

Continental glacier

ice sheet that covers large landmasses (Greenland, Antarctica)

Mass Movement

sudden movement of earth materials by gravity

What are examples of mass movement?

landslides, mudslides, avalanches, rock slides, debris flow, creep, slump

Soil

formed from the weathering of rocks and organic activity

What is soil composed of?

loose rock fragments and clay derived from weathered rock mixed with organic material

Soil Horizons

a layer of soil that has identifiable characteristics produced by chemical weathering and other soil forming processes

What are the horizons in order?

Oakes Always Eats Burritos, Crazy Right?

O-Horizon

made up of humus (decomposed organic matter)

A-Horizon

(topsoil) seeds and plant roots grow in this dark-colored layer

E-Horizon

leaching layer (minerals pass down to next layer by water)

B-Horizon

(subsoil) contains clay and mineral deposits

C-Horizon

broken up parent material (regolith)

R-Horizon

bedrock