1. Changes to Earth’s Surface

2. Layers of the Earth

3. Constructive vs. Destructive Forces
Constructive Forces build up features on the surface of the Earth.
Destructive Forces break down features on the Earth’s surface.
Mt. Everest
Niagra Falls

4. Destructive Forces Identify examples of surface features caused by destructive processes.
Destruct means to destroy or break down.
Examples…
Weathering (chemical or mechanical)
Erosion (water - rivers and oceans, wind)
Impact of organisms
Earthquake

5. Destructive Force: Weathering
The process of breaking down of rocks and land due to forces such as gravity, wind, water and ice. When it rains, rocks are washed down a mountain or down a stream. Soils are washed away. The ocean beats against a cliff and breaks it apart. Wind causes rock to wear away as it blows sediment through the air.

6. Destructive Force: Erosion
When rocks and sediment weather and move elsewhere, this movement is called erosion. The process is caused by water, ice, wind or gravity moving pieces of rock and soil.

7. Destructive Force: Mechanical Weathering
Mechanical weathering (physical weathering) is the process of breaking rock and sediment into smaller pieces. For example…
Temperature…cool nights and hot days causes water in the rock to expand and contract
Flowing rivers and streams
Roots and plants also pushing into the rocks
Animals burrowing and digging

8. Destructive Force: Mechanical Weathering from Flowing Water
When water in rivers, streams, and waterfalls move over rock it weathers—breaking into smaller and smaller pieces.

9. Destructive Force: Erosion from Flowing Water
Rivers, streams, and runoff carry weathered rock or soil to another place. Fast moving streams and rivers will carry big and small rocks downstream. Slower moving water carries smaller rocks and soil downstream. This moving water causes soil erosion—carrying the soil away to a different location.

10. Destructive Force: Erosion from Flowing Water forms Canyons
Canyons are large valleys created by a river or stream. This simple animation shows how the Colorado River has "cut down" into the rock layers of the Grand Canyon, creating a deep valley wit steep walls. This is created over thousand of years. Canyons demonstrate both weathering and erosion.

11. Mechanical Weathering and Erosion
Destructive Force:
Mechanical Weathering and Erosion
due to Gravity
As rocks slide down a hill or mountain, they break other rocks into smaller pieces.

12. Destructive Force: Mechanical Weathering and Erosion from Water and Gravity
Sometimes a side of the hill is washed away by running water after a lot of precipitation. The soil and rocks move down the hill in a landslide or mudslide. Watch this landslide in the Alps…
Watch Mt. St. Helens Erupt on May 18th, 1980…

13. Destructive Force: Mechanical Weathering and Erosion from Water and Gravity

14. Destructive Force: Mechanical Weathering and Erosion by Wind
As the wind blows it picks up small particles of sand and blasts large rocks with the abrasive particles, cutting and shaping the rock.

15. More Mechanical Weathering and Erosion
by Wind
Strong winds can move small rocks and soil from one location to another. Blowing wind and sand are the reasons these rocks and dunes have formed.

16. Destructive Force: Mechanical Weathering and Erosion From Water and Ice
Water in cracks in the rock freezes. As it freezes it expands causing the rocks to break. This is known as ice wedging.

17. Destructive Force: Mechanical Weathering and Erosion From Wind, Water, and Ice
Land is being constantly worn down by wind, water, and ice.
The original level of the plateau.

18. Destructive Force: Mechanical Weathering and Erosion by Glaciers (Ice)
Glaciers are formed over many years as large amounts of snow fall and accumulate. The snow compacts and changes to ice. Stuck in the bottom of the glacier are stones of various sizes that wear away the rock under the glacier as it moves downhill. It is considered a large river of ice that moves very slowly downhill.

19. Destructive Force: Mechanical Weathering and Erosion by Glaciers (Ice)
Striations or scratches made in the rock under a glacier by the stones stuck in it as the glacier moved downhill. Click on the link…

20. Destructive Force: Mechanical Weathering and Erosion by Glaciers (Ice)
The weathering and erosion from glaciers create large U-shape valleys, which take thousands of years to create. Watch this glacier weather and erode the land over time…

21. Destructive Force: Mechanical Weathering and Erosion By Plants and Animals
Plant roots break apart rocks. Animals burrow breaking up and moving rock and sediment.

22. Destructive Force: Chemical Weathering
Chemical weathering includes the effect of weathering on molecules and atoms. For these chemical reactions to happen in nature, moisture, and heat must be present. Water, oxygen, carbon, and other chemicals in the atmosphere are the main reasons for chemical weathering.

23. Destructive Force: Chemical Weathering Due to Acid Rain

24. Destructive Force: Chemical Weathering Due to Plants and Animals
Chemical weathering would include the effect of animals and plants on the landscape. This is more than roots digging in and wedging rocks. This is also considered biological weathering, which is the actual molecular breakdown of minerals.

25. Destructive Force: Mechanical and Chemical Weathering

26. Destructive Force: Earthquakes
An earthquake results from the sudden release of stored energy in the Earth’s crust. It is caused by a strain on the fault lines of the Earth’s crust. When the energy of the strain is released, the earthquake occurs. At the Earth's surface, earthquakes cause a shaking or displacement of the ground and sometimes cause the ground to break apart and change shape. Transforming and converging boundaries often result in destructive changes to Earth’s surface. Earthquake Animation!

27. Destructive Force: Earthquakes

28. Destructive Force: Earthquakes
Not only do buildings collapse when an earthquake hits, but the land itself changes. Visible changes appear when one block of land has moved compared to another. Roads often change their placement by becoming uneven or cracked. Streams can also change course. Sometimes rocks fall and block a stream. Other times, the land is lowered in certain areas which makes it easier for the water to flow in the new direction.

29. Destructive Force: Earthquakes
The San Andreas Fault line is 810 miles and runs along California. It separates the tectonic boundary of the Pacific and North America boundary. They are transforming boundaries.

30. Constructive Forces Identify surface features caused by constructive forces.
Construct means to build up.
Constructive Forces build up features on the surface of the Earth.
Sediment (Deltas, sand dunes, etc.)
Tectonic Plates Colliding (Mountains)
Crust deformation (Folding or Faulting)
Volcanoes (makes Islands)

31. Constructive Force: Deposition of Sediment
The process of sediment being carried and deposited , which creates new landforms.
Wind – sand transported by the wind creates sand dunes.
Water – bits of soil and rock can be carried downstream and deposited causing deltas.
Ice – glaciers pick up and move rock and other materials, depositing it elsewhere.

32. Constructive Force: Deposition of Sediment
By Wind
Sand is carried and deposited creates a sand dune.

33. Constructive Force: Deposition of Sediment
By Water
Amazon River Delta into the Atlantic Ocean
Mississippi River Delta into the Gulf of Mexico
Sediment is carried and deposited at the mouth of a river creates a delta.

34. Constructive Force: Deposition of Sediment
By Glaciers (Ice)

35. Constructive Force: Tectonic Plates
Mountains and ridges can be formed because of moving tectonic plates. Watch this…

36. Constructive Force: Tectonic Plates
The Rockies, Andes, and Himalayas Mountain Ranges formed from plates colliding. This is called a convergent boundary.

37. Constructive Force: Tectonic Plates
Mid-Atlantic Ridge or the Great Rift Valley form from plates separating. This is called a divergent boundary.

38. Constructive Force: Faults and Folding
Faults are cracks in the Earth’s crust. The surface of the Earth is made up of tectonic plates that are floating on magma (molten rock). It is along these fault lines that earthquakes and volcanoes occur.

39. Constructive Force: Volcanoes
A volcano is an opening in the Earth's surface or crust, which allows hot, molten rock, ash and gases to escape from deep below the crust of Earth’s surface.
Volcanic activity form mountains and land over time.
Magma hot molten rock within volcano. Lava flows from the volcano on Earth's surface. It cools to form igneous rock.

40. Constructive Force: Volcanoes
There are two main types of volcanoes: shield and composite.
Shield volcanoes are usually found in the middle of tectonic plates. Magma moves out a hole in the middle of the plate piling lava on Earth’s surface, and slowly building a mountain of rock. Ex. Hawaiian Islands
Composite volcanoes erupt less often and are more violent when they do erupt. Ex. Mt. St. Helens

41. Constructive Force: Volcanoes

42. Constructive Force: Volcanoes

43. Constructive vs. Destructive Forces
What are two examples of destructive forces? Give an example of a slow and fast destructive force.
What are four examples of constructive forces? Give an example of a slow and fast destructive force
Give an example where constructive and destructive forces work together to create a landform.