Section 3 From Bedrock to Soil

The Source of Soil

• Soil is a loose mixture of rock fragments, organic material, water, and air that can support the growth of vegetation.

• Not all soils are the same. Because soils are made from weathered rock fragments, the types of soil that forms depends on the type of rock that weathers.

• The rock formation that is the source of mineral fragments in the soil is called parent rock.

Chapter 7

Section 3 From Bedrock to Soil

The Source of Soil, continued

• Bedrock is the layer of rock beneath the soil.

• Sometimes, the bedrock is the parent rock if the soil above it formed from the bedrock below. Soil that remains above its parent rock is called residual soil.

• Soil that is blown or washed away from its parent rock is called transported soil.

Chapter 7

Chapter 17

Wave Energy

• When waves crash into rocks over long periods of time, the rocks are broken down into smaller and smaller pieces until they become sand.

• Waves usually play a major role in building up and breaking down the shoreline. A shoreline is the boundary between land and a body of water.

Section 1 Shoreline Erosion and Deposition

Chapter 17

• As wind moves across the ocean surface, it produces ripples called waves. The size of a wave depends on the strength of the wind and how long the wind blows.

• The wind that results from summer hurricanes and severe winter storms produces large waves that cause dramatic shoreline erosion.

Section 1 Shoreline Erosion and Deposition

Wave Energy, continued

Chapter 17

•Wave Trains Waves travel in groups called wave trains. When wave trains reach shallow water, the bottom of the wave drags against the sea floor, slowing the wave down.

• The upper part of the wave moves more rapidly and grows taller, and begins to curl and break. These breaking waves are known as surf.

• The time interval between breaking waves is called the wave period.

Section 1 Shoreline Erosion and Deposition

Wave Energy, continued

Chapter 17

Wave Period of Ocean Waves

Section 1 Shoreline Erosion and Deposition

Chapter 17

• The Pounding Surf Tremendous energy is released when waves break. Crashing waves can break solid rock and throw broken rocks back against the shore.

• Breaking waves also wash away fine grains of sand, which are picked up by the waves and wear down and polish coastal rock.

• The process continues until rock is broken down in smaller and smaller pieces that eventually become sand.

Section 1 Shoreline Erosion and Deposition

Wave Energy, continued

Chapter 17

Wave Erosion

• Shaping a Shoreline Wave erosion produces a variety of features along a shoreline.

• Sea cliffs are formed when waves erode and undercut rock to produce steep slopes.

• The next two slides show some of the major features that result from wave erosion.

Section 1 Shoreline Erosion and Deposition

Chapter 17Section 1 Shoreline Erosion and Deposition

Chapter 17Section 1 Shoreline Erosion and Deposition

Chapter 17

Wave Deposits

• Beaches are areas of the shoreline made up of material deposited by waves. Some beach material is also deposited by rivers.

• Waves carry a variety of materials, including sand, rock fragments, dead coral, and shells.

• The colors and textures of beaches vary because the type of material found on a beach depends on its source.

Section 1 Shoreline Erosion and Deposition

Chapter 17

• Wave Angle and Sand Movement Waves moving at an angle to the shoreline push water along the shore and create longshore currents.

• Longshore currents move sand in a zigzag pattern along the beach.

Section 1 Shoreline Erosion and Deposition

Wave Deposits, continued

Chapter 17

• Offshore Deposits When waves erode material from the shoreline, longshore currents can transport and deposit the material offshore, which creates landforms in open water.

• A sandbar is an underwater or exposed ridge of sand, gravel, or shell material.

• A barrier spit is an exposed sandbar connected to the shoreline.

Section 1 Shoreline Erosion and Deposition

Wave Deposits, continued

Chapter 17

Glaciers—Rivers of Ice

• A glacier is a large mass of moving ice. They are capable of eroding, moving, and depositing large amounts of rock materials.

• Glaciers form in areas so cold that snow stays on the ground year-round. Because glaciers are so massive, the pull of gravity causes them to flow slowly, like “rivers of ice.”

Section 3 Erosion and Deposition by Ice

Chapter 17

• Alpine Glaciers form in mountainous areas. One common type of alpine glacier is a valley glacier.

• Valley glaciers form in valleys originally created by stream erosion. As these glaciers slowly flow downhill, they widen and straighten the valleys into broad U shapes.

Section 3 Erosion and Deposition by Ice

Glaciers—Rivers of Ice, continued

Chapter 17

• Continental Glaciers are huge, continuous masses of ice that can spread across entire continents.

• The largest continental glacier in the world covers almost all of Antarctica. This ice sheet is approximately one and a half times the size of the United States, and is more than 4,000 m thick in some places.

Section 3 Erosion and Deposition by Ice

Glaciers—Rivers of Ice, continued

Chapter 17

• Glaciers on the Move When enough ice builds up on a slope, the ice begins to move downhill. Thick glaciers move faster than thin glaciers, and the steeper the slope, the faster the glaciers will move.

• Glaciers move in two ways: sliding and flowing. A glacier slides when its weight causes the ice at the bottom to melt. A glacier flows as ice crystals within the glacier slip over each other.

Section 3 Erosion and Deposition by Ice

Glaciers—Rivers of Ice, continued

Chapter 17

Movement of Glaciers

Section 3 Erosion and Deposition by Ice

Chapter 17

• Glacier movement is affected by climate. As the Earth cools, glaciers grow. About 10,000 years ago, a continental glacier covered most of North America.

Section 3 Erosion and Deposition by Ice

Glaciers—Rivers of Ice, continued

Chapter 17

Landforms Carved by Glaciers

• Continental glaciers and alpine glaciers produce landscapes that are very different from one another.

• Continental glaciers smooth the landscape by scraping and eroding features that existed before the ice appeared.

• Alpine glaciers carve out large amounts of rock material and create spectacular landforms.

Section 3 Erosion and Deposition by Ice

Chapter 17Section 3 Erosion and Deposition by Ice

Chapter 17

Types of Glacial Deposits

• As a glacier melts, it drops all the material it is carrying. Glacial drift is the general term used to describe all material carried and deposited by glaciers.

• Glacial drift is divided into two main types, till and stratified drift.

Section 3 Erosion and Deposition by Ice

Chapter 17

• Till Deposits Unsorted rock material that is deposited directly by the ice when it melts is called till. Unsorted means that the till is made up of rock material of different sizes.

• The most common till deposits are moraines. Moraines generally form ridges along the edges of glaciers.

Section 3 Erosion and Deposition by Ice

Types of Glacial Deposits, continued

Chapter 17

• Stratified drift is a glacial deposit that has been sorted and layered by the action of streams or meltwater.

• Streams carry sorted material and deposit it in front of the glacier in a broad area called an outwash plain.

• Sometimes, a block of ice is left in an outwash plain when a glacier retreats. As the ice melts, sediment builds up around the block of ice, forming a depression called a kettle.

Section 3 Erosion and Deposition by Ice

Types of Glacial Deposits, continued

Chapter 17

Glacial Drift: Stratified Drift and Till

Section 3 Erosion and Deposition by Ice