Earth Space Science Chapter 5

sunday 10.20.26

What is mechanical weathering?

Breaking rocks into smaller pieces without changing their composition.

What are the three main types of mechanical weathering?

Frost wedging, unloading, and biological activity.

What is frost wedging?

Water freezes in cracks, expands, and breaks rocks apart.

What happens to water when it freezes?

Its volume increases by about 9%.

What is unloading?

Pressure on rock decreases, causing outer layers to expand.

What is exfoliation?

Outer rock layers peel away like layers of an onion.

What is biological weathering?

Living things, such as growing roots, break rocks apart.

What is chemical weathering?

Rock changes into new substances through chemical reactions.

What are the weathering products of quartz and feldspar?

Quartz leaves quartz grains and feldspar forms clay minerals.

What gases commonly cause acid rain?

Sulfur oxides and nitrogen oxides.

What is the most important agent of chemical weathering?

Water.

What is oxidation?

Oxygen reacts with iron-containing minerals and forms oxides or rust.

What acid forms when carbon dioxide mixes with water?

Carbonic acid.

What are common examples of chemical weathering? (processes)

Rusting, limestone dissolving, and feldspar turning into clay.

What are real-life examples of chemical weathering? (examples of objects)

Worn marble gravestones and acid-damaged stone buildings.

What is spheroidal weathering?

Chemical weathering that rounds rock corners and edges.

What three factors affect the rate of weathering?

Surface area, rock characteristics, and climate.

How does breaking rock into smaller pieces affect weathering?

It exposes more surface area and speeds chemical weathering.

Which climate causes the fastest chemical weathering?

Warm, wet climates.

Which rock type is generally less resistant to weathering?

Sedimentary rocks, especially limestone.

Why does marble chemically weather faster than granite in weak acid?

Marble contains calcite, which dissolves in weak acid.

What is residual soil?

Soil formed directly from the bedrock beneath it.

What is transported soil?

Soil formed from material moved from another location.

What is the most important factor in soil formation?

Climate.

In which climates does soil generally form quickly?

Warm, wet climates.

What is soil texture?

The proportions of sand, silt, and clay in soil.

What are soil particle sizes from smallest to largest?

Clay, silt, sand.

How do you read the soil texture diagram?

Follow sand, silt, and clay percentages to where their lines meet.

What are the main sources of organic matter in soil?

Dead plants, animals, and their decomposed remains.

What is humus?

Decayed organic matter that adds nutrients and helps hold water.

What is the A horizon?

Topsoil containing mineral and organic matter.

What is the B horizon?

Subsoil where clay and minerals accumulate.

What is the C horizon?

Partially weathered parent material above bedrock.

What is pedalfer?

Soil found in humid temperate areas, rich in iron and aluminum.

What is pedocal?

Soil found in dry areas, often containing calcium carbonate.

What is laterite?

Hot, wet tropical soil rich in iron and aluminum oxides but poor in nutrients.

Why is laterite often poor for farming?

Heavy rainfall washes nutrients out of the soil.

How do today's soil erosion rates compare with the past?

Erosion is often faster today because humans remove vegetation.

Which human activities increase soil erosion?

Farming, logging, construction, and removing vegetation.

What is sheet erosion?

Water carries away thin layers of soil over a broad area.

What is the difference between sheet erosion, rills, and gullies?

Sheet erosion removes thin layers of soil; rills are small channels; gullies are large, deep channels.

What is mass movement?

The downhill movement of rock and soil due to gravity.

What force causes mass movements?

Gravity.

When are mass movements often most likely to happen?

During heavy rains and spring snowmelt when soil becomes saturated.

What four factors commonly trigger mass movements?

Water, oversteepened slopes, loss of vegetation, and earthquakes.

What is the difference between a rockfall and a rockslide?

Rockfalls fall through air, while rockslides move on inclined surfaces.

What is a slump?

A block of material moving downhill along a curved surface.

How do mudflows and earthflows differ?

Mudflows move quickly with lots of water, while earthflows move more slowly.

What is creep?

The slowest mass movement, gradually moving soil downhill.

What climate conditions favor mechanical weathering?

Cold and wet

Which season of the year poses the greatest threat of mass movements?

Spring

Which soil is common in the eastern United States?

Pedalfer.

Which soil is common in the drier western United States?

Pedocal.

Which soil is common in tropical regions?

Laterite.