How Water Shapes The Earth

How Water Shapes The Earth

10.4

By: Thomas Curalli & Ethan Tsui

List of Resources

Sandner, Lionel, Donald Lacy, Josef Martha, and James Milross. BC Science 8. Whitby, Ontario: McGraw-Hill Ryerson, 2006. 386-95. Print.

Google Images

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Definition

In geology, the process in which eroded sediments and other material are dropped or left by water or ice, creating built-up landforms such as deltas and eskers.

Deposition Part 2

By Water

Deposition Part 3

By Ice

This diagram shows the Fraser River Delta in Vancouver. Notice the fan shape.

When glaciers finish their journey they start to melt. Having acted almost like a piece of sandpaper, they have picked up many materials along the way. When they melt they deposit all of these materials. The next page shows some notable glacier-deposited features.

Different Features Deposited by a Glacier

Large boulder deposited on the ground by a glacier

Winding ridge of material deposited by a stream flowing under a glacier

Erratic

Esker

Fast moving water picks up sediment as it flows to the ocean. Once it reaches the ocean it slows down and deposits the sediments to form a delta. These are often fan-shaped or triangular.

Material deposited by water from melting glaciers

Ridge of rocky material deposited by a glacier. Moraines can be found at the sides and farthest advance of a glacier

Outwash

Moraine

Deposition

Delta formed by deposition

Definition

When rocks are weak and broken into smaller pieces those pieces are taken away from their main location. This process is called Erosion. The are two main agents of erosion: Moving water and glaciers. They work closely with gravity.

Erosion Part 2

Moving Water

Moving water physically breaks rock and material down into small pieces called sediment. Sediment can be carried large distances by the water and dropped in large amounts elsewhere. Water can make its way through cracks and physically weather things down.

Water eroding rocks in its path

Erosion Part 3

Gravity

An example of a landslide

When water or rain wets the slopes of a mountain or hill, other rock and material may become very heavy and unable to resist the force of gravity acting on them.

Erosion Part 4

Before

Glaciers

After

Glaciers have shaped much of BC's Landscape. 10,000 years ago, when the province was buried in sheets of ice, some parts of BC were almost 2000m deep in ice. As the ice was being pulled downhill by gravity it scraped and carved the land it passed over. Scratch marks or striations were left on rocks. Since glaciers were so large they were able to grind out entire valleys. The shape of these valleys looks like the letter "U".

Types of Valleys Shaped by Glacier

This can result in a large part of a hillside or mountain falling away and sliding downward.

Before

Rivers in high mountainous areas have high energy and carve valleys which look like the letter "V". When a river channel is rocky and steep, rapids are formed. Rapids are parts in water that move very quickly over exposed pieces of rock.

Arete : Narrow ridge between two cirques

Cirque: Bowl Shaped valley a the head of a glacier

Fiord: A narrow inlet of ocean between steep cliffs carved by glaciers

After

Horn: Pyramid shaped peak located between three cirques

Hanging Valley: U-shaped valley cut off by a bigger valley created by a larger glacier

Rapid movement of rock material down a slope of a hill or a mountain is called a landslide. An avalanche can be the same thing but involving ice or snow.

Erosion

Rocks causing water to be white and bubbly

This is why it looks wild because the rocks cause the water to go up and down. These parts of rivers erode the landscape quickly. The rivers in areas that are flat have lower energy and erode material by carving big curves in their banks.

Chemical Weathering

This occurs when a chemical reaction causes rock to break down or decompose. When chemical weathering occurs, the minerals in the rocks change their make-up and the rock becomes weaker.

Watch This Clip On How Caves and Sinkholes are Formed

Chemical Weathering Part 4

When rainwater mixes with carbon dioxide (CO2) in the atmosphere, or carbon from organic materials on the ground the water becomes acidic. When the rain falls and becomes ground water, if the acidic water comes in contact with any rocks with calcium carbonate in them, the carbonate rock will start to dissolve. These small gaps will get bigger and bigger over thousands of years and this is how underground caves are formed.

Chemical Weathering Part 2

If a cave is formed close to the surface and the carbonate rock forming the cave collapses, a sink hole will be the result. A landscape with many sinkholes is called a karst.

Karst Landscape

Chemical Weathering Part 3

Chemical weathering also happens when a plant dies and decomposes. The chemicals released by the plant work to break down the rock they are lying on. A type of moss called lichen has roots that release chemicals that slowly break down the rock underneath the plant.

Lichen

Chemical weathering is the greatest in places with climates with high temperatures, high levels of pollution and lots of rainfall. Water and oxygen in the atmosphere can cause chemical reactions that break down the minerals making up rocks. Rust is a result of chemical weathering. When moisture in the air reacts with iron it can cause it to rust or oxidize.

Rust may form on your bike or car

Caves can be the result of chemical weathering

Physical Weathering

In physical weathering rocks are broken down physically. This means that rocks can be scratched to bits when hit by harder rocks. The wind could blow harder rocks against softer rocks.

Physical Weathering Part 3

Physical Weathering Part 2

Physical Weathering happens the most in climates with a lot of moisture in the air, or if there is a lot of rain and snow. Also this can happen when there are large temperature changes between the seasons or throughout the day.

When water in the cracks and pores of a rock freezes, the ice expands breaking the rock in half or into more cracks. This type of physical weathering is called ice or frost wedging. This is common in BC.

Definition

Weathering is the gradual process of breaking down rock into smaller fragments. There are two main types of weathering: Physical Weathering and Chemical Weathering

Weathering