Post on 28-Nov-2014
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Tear it downBuild it up
Constructive and Destructive Processes
Chapter 1 Lessons 2 and 3Textbook Pages 22-41
Let’s focus on Destructive Processes first…
Words to know Weathering Erosion Sediment Organisms Earthquake Volcano
Destructive ProcessesDestructive Processes are when things happen to the earth that destroy or break down part of it. One example of a destructive process is a river wearing away the rocks and dirt to form a canyon.
In the story, an example of a destructive process was the erosion that carried the dirt and the minerals from rocks down into the cave.
WeatheringWeathering is the process that breaks rocks down into pieces called sediment. There are two types of weathering.
Mechanical Breaks larger rock into smaller pieces called sediment
Water trickling in between cracks in rocks, freezing, and breaking the rocks apart
Blown sand or rushing water Plant roots Burrowing animals
Chemical Minerals that make up rocks are dissolved
Weak acids from water and chemicals in the air or soil Dissolve limestone and marble easily The minerals are not necessarily dissolved completely.
Erosion
Weathering breaks rock into sediment. Erosion is the process of that sediment being carried away by moving water, wind, or moving ice.
Some examples of causes for erosion are
Water moving down a river
Glaciers moving Ocean waves and
currents Wind
Erosion, cont.As they transport sediment from one place to another, erosion can cause
Wider and deeper rivers Valleys Canyons Transformation from V-
shaped river valley to U-shaped river valley
Why do you think this is? Lakes Sea caves
Grand Canyon
Earthquakes
Volcanoes
Mount St. Helens
Top: August 1979
Bottom: May 1980
OK… What about constructive processes?
Words to know Deposition Earthquakes Volcanoes Faults
Constructive ProcessesConstructive processes are processes that happen to the earth that build it up. One example of a constructive process is when sand is deposited on a river bank by the running water. The sand gathers, and builds the river bank up, making it higher.
In the story, an example of a constructive process was the stalactites that grew from the deposition of the minerals.
Deposition
Think back for a second… Weathering Erosion
You have learned how rocks are broken apart by weathering into sediment. Then the sediment is carried away by erosion. The sediment doesn’t just disappear, though. It is deposited in a new place. That’s called deposition.
Deposition, cont.
Where can you see evidence of deposition?
At the mouth of a river
On flood plains (from the flooding of rivers)
Curves of a river (p. 35)
Alluvial fans (p. 35) Deltas
delta
Earthquakes
Volcanoes
Mauna Loa – A Hawaiian island formed by shield volcanoes.
Did I make a mistake?Wait a minute… Did you notice that I listed earthquakes and volcanoes twice? Some processes can be a combination of constructive and destructive. They build the earth up in some ways, and destroy it in others.
Volcanoes Earthquakes
How are volcanoes constructive processes?How are they destructive processes?
Links for more information
Forces of Naturehttp://www.nationalgeographic.com/forcesofnature/