Weathering and Erosion PowerPoint

Created By: Allison, Brianna, & Jade

WeatheringWeathering is the process where rocks and other

materials on the Earth’s crust are broken down. Weathering is a slow yet continuous process that, as a result, is hard to notice at times. But, peeling paint

and the contrast between bright red, sharp edged bricks and dull red, smooth edged bricks are a few of the places where weathering is very noticeable and

easy to pick out.

Mechanical Weathering• Mechanical weathering is when

rocks are broken down into smaller shapes and pieces that will eventually turn into soil.

• At the beginning of the weathering process, the rocks are sharp and angular.

• Eventually the rocks become smooth and rounded as the weathering process continues.

• All of the different agents (causes) of weathering result in the breaking down of rocks.

Agents of Mechanical Weathering

1. Temperature: During the day when the Sun is out, rocks become hotter and expand. During the night when the Sun is no longer out, the rocks will become cooler and contract. That continuous process is known as exfoliation and causes small pieces of the rocks to flake off.

2. Frost Action: Water will go into cracks in rocks and when it gets cold enough outside (32 degrees F or 0 degrees C), the water inside the rocks will freeze. That will cause the water, and then the rock to expand, causing the rock to eventually break into pieces.

3. Organic Activity: Root-pry is when a plant starts growing in the crack of a rock, and as it continues to grow, it will eventually cause the rock to break apart.

4. Gravity: Gravity will pull loose rocks and soil down a slope, causing a landslide where the tumbling rocks will bump into other rocks on the way down and break into smaller pieces.

5. Abrasion: Sand that is blown by wind causes abrasion where rocks are worn down by particles that get carried by wind and water and scrape exposed rocks, making them smoother.

Chemical Weathering

• Chemical Weathering is a type of weathering where the chemical makeup of rocks changes.

• During chemical weathering, rocks are broken down in a process called decomposition (process where dead organisms are broken down), or minerals are added or taken away from rocks.

• Acid rain and pollution are two factors of chemical weathering that cause the most damage, as you can see from the picture at the right. Prince Edward’s Island

Agents of Chemical Weathering1. Water: Water can do three main things: dissolve the crucial minerals in rocks that hold them

together, speed up the decomposition process using acids, and create a completely different material when water is combined with certain minerals.

2. Oxidation: Oxidation is when oxygen combines chemically with some other substance, eventually creating a new substance. Oxidation can actually create rust, too. So, chemical weathering is caused by oxidation.

3. Carbonation: Carbonation is when chemical reactions occur between certain substances and carbonic acid, which is an acid that comes from carbon dioxide when it dissolves in water. Carbonic acid can be found in rain, that will seep into rocks on the ground and won’t actually do too much damage, but it does slowly decompose certain rocks like limestone and feldspar.

4. Sulfuric Acid: Along with carbonic acid, sulfuric acid can be found in acid rain. But, unlike carbonic acid that is a relatively weak acid, sulfuric acid is very strong and can wear down rocks and even metal at a quick rate. Sulfuric acid is created from burning coal.

5. Plant Acid: So not only can plant acid be an agent of mechanical weathering, but it can also be an agent of chemical weathering. Plants actually do produce acids, but similar to sulfuric acid, plant acids are very weak. But, they do dissolve some minerals in rocks causing the rock to break into pieces over time.

ErosionErosion is the process where weathered rocks and particles of soil are moved over land. After the rocks are broken down from weathering,

erosion carries that sediment and deposits it in a new location. That process is called deposition, and along with erosion, contributes to changing

the shape of our Earth.

Mount Saint Helens

Five Types of ErosionGravity

Glaciers

Wind

Waves Running Water

Weathering and Erosion in New England

Gravity

• Gravity is what pulls down rocks and soil (sediment) down slopes• That process is called mass wasting and it can happen quickly or

slowly. Landslides and mudslides are examples of mass wasting.• A landslide happens due to an earthquake or volcanic eruption, and

is when soil, rocks, and boulders fall down a slope. It causes a lot of damage in the end, as it moves anything in its path.

• A mudslide happens after heavy rain when rain turns soil into mud and then mud starts flowing down hills. As it descends down hills, the mud becomes thicker and thicker and pummels through anything it reaches.

• Those two examples are slow examples of mass wasting.

Wind• Wind is one of the most active agents of erosion, especially in beaches,

fields, and deserts.• Loose materials on the ground in these areas are easily picked up by wind

and can land anywhere.• Earth’s surface is eroded by wind in two ways: deflation and abrasion.• Deflation is when loose sand, silt, and clay is moved by wind over short

distances.• Abrasion is when larger pieces of sediment bounce along the ground as they

are moved by wind. As they do so, wear away rocks on the ground that they hit by cutting and polishing them down.

• Wind forms sand dunes, which are large hills of sand deposited by wind.• Wind also forms loess, which are fertile areas of silt and sand that were

blown by huge gusts of wind. They are the particles that didn’t get deposited in sand dunes.

Glaciers• A glacier is a huge piece of ice and snow that moves, and this type

of erosion is one of the most powerful types.• Ice from glaciers is eroded by being plucked away from the rocks

underneath it, and by the process of abrasion.• When a glacier pummels through a valley, anything in its path is

taken with it. Those rocks, boulders, and anything else in its path is called glacial debris.

• As the glacier moves with this load of debris, the surface of the land it’s traveling over grinds and polishes down the land.

• So glacial erosion scrapes away anything it travels over and can even form mountains.

Running Water• Running water is the major cause of erosion and has the biggest effect on our

Earth than any other type of erosion.• Rivers, rain, streams, and runoff (water that flows over the surface of the

Earth) are three types of running water that perform erosion.• When there’s a lot of rainfall, there is a greater amount of runoff. Runoff will

carry particles of clay, sand, and gravel over land downhill through the water.• That sediment will form grooves in the soil called rills that become wider over

time and will eventually form into gullies which are channels for runoff.• The amount of runoff is also affected by the amount of plant growth where

places with little plant growth have greater erosion since there are less roots to hold soil in place.

• The soil is what absorbs the water and causes the erosion.

Waves• Waves are caused by earthquakes, tides, and winds.• They are very powerful and are constantly changing the shape of

shorelines through erosion.• There are many ways that waves erode away the shoreline.• They carry small rocks and sand that chip off pieces of the

shoreline.• When water is forced into cracks along the shoreline, the increased

pressure makes the cracks become larger and eventually break.• Salt in water dissolves rocks, which is another type of erosion.• The size and force of the waves also affects the rate of

erosion.

Weathering and Erosion in New England

Old Man of the Mountain Hurricane Bill

Plum IslandWilbraham Mountains

Bibliography

Old Man of the MountainThe Old Man of the Mountain was a granitic rock formation with the profile of a face sticking out of a mountain. The Old Man of the Mountain was located in Franconia Notch State Park in New Hampshire in the White Mountains. It was formed an estimate of 2,000 to 10,000 years ago and it was formed at the end of the glacial period by glaciers that were melting and rubbing up against the Franconia Mountains (part of the White Mountains).So the weathering of that mountain led to erosion that formed a cliff that eventually eroded into the Old Man of the Mountain. In May of 2003, the renowned formation collapsed to the ground. Heavyrains, high winds and freezing temperatures had caused much wear on the mountain for a while before it collapsed, so it had been reinforced with cables and spikes, but they weren’t enough. All of that weathering caused the cliff to be eroded down to a much flatter mountain side.

Hurricane BillHurricane Bill was the fifth largest Atlantic hurricane ever and traveled along the eastern coast of the USA and Canada in August of 2009. Hurricane Bill was a category 4 hurricane at one point, but it started decreasing in intensity as it passed by Bermuda, and continued to decrease during the rest of its journey too. When it passed by Massachusetts, it was a category 1 hurricane, meaning it was the least intense and least destructive of the five categories of hurricanes possible. The hurricane caused severe rain in MA, that caused a great amount of weathering, leading to changes in the Earth’s surface in those areas along the coast and beaches. Erosion, especially in beaches in New York, was a major factor of the hurricane that resulted in the loss of some animal habitats, flooding, and much more.

Plum Island

On Plum Island, the extremely quick rate of erosion is putting people’s homes along the coast in danger. Sand deposits are supposed to go to the beach and replenish the land with new sand. That sand will then make up for all the lost sand from erosion, but for the past ten years, that hasn’t been happening, therefore causing a major erosion problem. Wind and water are also causing erosion along the beach where loose sand that isn’t being stored by vegetation or fences gets taken by the wind or water away from the beach. Large waves that hit the beach remove sand from the beach and carry it through the water.

Wilbraham MountainsThe Wilbraham Mountains, located in Wilbraham, MA take up most of the town. The Wilbraham Mts. were formed by melting glaciers. The mountains are made up mostly of Amherst schist and much erosion of the mountains hasn’t taken place there in a while. During most of the erosion, metamorphism would loosen up rocks that would eventually tumble down the mountains. On the east side of this mountains range, part of rock had been weathered to a gray color. Back in the Triassic Period (roughly 250 million years ago), weathering and erosion carried sediment into the Connecticut Valley Lowlands. Today, the sediment is made of akrose, sandstone, and shale and is either a red or grayish color.

Global Warming Global Warming is thought to be the cause of increasing temperature, along with precipitation and flooding in New England. In June 1998, the record for the most rainfall in a year was broken, causing rivers and streams to become much larger. That caused the Earth’s surface to break down through weathering and erosion and even led to the closure of Logan Airport and a few highways at one point. Vermont, New Hampshire, Rhode Island, and Massachusetts each received more than double their normal monthly rainfall. The graph to the right shows how the temperature increased over the past 30 years. In 2006, that summer was the second hottest summer on record in Massachusetts. That caused mechanical weathering in Massachusetts, where rocks were broken down, due to a cycle of heating and cooling that leads to parts of the rock flaking off. That caused a change in the earth’s surface.

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