The state of Georgia wants you to…

1. The state of Georgia wants you to… • Identify surface features caused by constructive and deconstructive processes.

2. Constructive vs. Destructive • Land forms are the result of a combination of constructive and destructive forces. Constructive forces affect the earth's surface by building it up to form new landforms like mountains and islands. Destructive forces affect the earth's surface by breaking down landforms to form new ones.

3. Deposition – deltas & sand dunes • The dunes are the product of the wind and rain eroding nearby mountains. The dunes collect here because the prevailing winds across the valley blow in this direction and meet winds blowing in the opposite direction. The sand drops to the valley floor and begins to collect. So over the course of millennia, the dunes have build. Tomorrow they will be different because the wind still blows, the sand still moves and the deposits of sand still grow.

4. Western Sand Dune

5. Delta • A delta is a low, watery land formed at the mouth of a river. It is formed from the silt, sand and small rocks that flow downstream in the river and are deposited in the delta. • A delta is often (but not always) shaped like a triangle (hence its name, delta, a Greek letter that is shaped like a triangle).

7. NASA view of a delta from space.

8. Faults • Faults are usually caused by the Earth's crust bending and breaking in the middle because of the forces pressing on it. These bends and breaks can form faults where the earth's crust is able to move.  • Faults also mark plate boundaries. There are three main types of faults and each are constructive in their own way.

9. Divergent Fault Line • Divergent Fault is where two plates are moving away from each other. (For more) • As plates pull apart from each other the earth's crust spreads apart. This usually causes rifts or rift valleys. The majority of this activity takes place deep within the oceans along plate boundaries. As the plates pull apart hot magma is pushed toward the surface and volcanoes occur. This affects the Earth's surface by adding new material to the surface.

10. Convergent Fault Line • Convergent Faultis when two plates come together. • Not only can this cause destruction it can also cause construction. When two plates collide in a collision zone the result is mountains. The pressure of these two plates hitting each other causes the crust of the earth to rise. This can occur in the oceans of the world and on land. Mountain building is a very slow process but it is caused by convergent faults.

11. Transform Faultis when two plates slide past each other. • Notice how the delta spreads in a fan shape.

12. Earthquakes • What is an earthquake?Earthquakes are the shaking, rolling or sudden shock of the earth’s surface. They are the Earth's natural means of releasing stress. More than a million earthquakes rattle the world each year.

13. Sometimes new landforms are created. Earthquakes can happen on land and in water. An earthquake can destroy everything that gets into its path. It destroys buildings, bridges, dams, and other structures. • Earthquakes most commonly occur along faults in the crust.   

14. Where do earthquakes happen?

15. Why? Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in slow but constant motion caused by the release to space of the heat in the Earth's mantle and core.

16. Why continued… The heat causes the rock in the Earth to warm so that the plates move slowly but surely. Plate boundaries lock as the plates move past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, an earthquake happens.

17. The West Coast is most at risk of having an earthquake, but earthquakes can happen in the Midwest and along the East Coast. Earthquakes can be felt over large areas although they usually last less than one minute. Earthquakes cannot be predicted - although scientists are working on it!

18. Quit pushing!!

19. Largest Fault in the US The San Andreas Fault

20. Natural Disasters - Earthquakes - Fault Lines

21. Technology and Earthquakes • Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph. Advances in seismograph technology have increased our understanding of both earthquakes and the Earth itself. • Perhaps the earliest seismograph was invented in China A.D. 136 by a m an named Choko.

22. Volcanoes • A volcano is a mountain or hill formed by the accumulation of magma or molten rock. Magma is typically produced at depths of 50 to 60 miles below the surface; because liquid magma is less dense than solid rock, it is pushed out of cracks in the Earth's surface. Volcanic eruptions can be deadly, damaging property and infrastructure.

23. Volcano Types • Volcanoes are one of the most powerful forces in nature. A volcano is a hole in the earth’s crust. The hollow holes that are in volcanoes are called craters. There are different types of volcanoes;  shield-volcanoes, cinder cone volcanoes, lava domes and the most common - composite volcanoes.

24. Volcanoes are basically hollowed-out mountains with connections to the Earth’s magma core. There are over 500 volcanoes in the world. The volcanoes are contained in a circle called theRing of Fire.

25. Volcanic eruptions start in a magma chamber. The high pressure of the steams and gasses make the magma fill the magma chamber. • When the chamber is full, the type of eruption depends on the amount of gases and silica in the magma. • The amount of silica determines how sticky the magma is and the amount of water determines the explosive potential of the steam.

26. Evidence of Steam & Magma

27. Volcanoes can form on land but they can also form in water. Volcanoes can help build up the Earth's surface (constructive) like the developing Hawaiian Islands, but volcanoes can also be very destructive to the Earth's surface.

28. Destructive Volcanoes • Volcanoes can endanger anything that happens to be in the vicinity of an erupting volcano such as humans, property, and agriculture.  • Volcanoes are destructive because when they erupt not only  can they spew hot ash and lava but they can also cause other destructive activities to occur.

29. Volcanic DiagramNotice the difference in destruction on either side of the volcano.

30. Mud flows also may occur with a volcano eruption engulfing everything in its path.. Volcanic Landslide step 1 • Volcanic Landslide step 2

31. Volcanoes are destructive because when they erupt not only  can they spew hot ash and lava but they can also cause other destructive activities to occur. • Lava flows can destroy homes, grass, trees, and anything else in its destructive path.   The lava which is hot melted rock flows from one place to another burning everything it touches.

32. Tsunamis and Earthquakes • Two main destructive forces can be triggered by a volcano: tsunamis and earthquakes. • Damage to the Earth's surface caused by a volcano is often not repairable but over many, many years some new growth may begin to appear.

33. Good Thing/Bad thing • There are many constructive properties of volcanoes. For example, volcanoes help the rock-cycle by bringing rocks to the surface to form new landforms like islands.  All of the Hawaiian Islands were created by volcanoes. There is even a new island forming right now.

34. Another example of a volcanoes' constructive force is that if there are enough eruptions or a constant lava flow a mountain can form. Some of these mountains form on land but many build from the bottom of oceans.

35. Here are other ways a volcano can be constructive... • volcanic ash can be used as an abrasive or cleaning agent • volcanic ash can act as a mulch • volcanoes can create geothermal energy • ashes can make more fertile soil • To see an animation of an erupting volcano  click here.

36. Erosion • Erosion is a process in which rock and soil are broken loose from the earth's surface at one location and moved to another.

37. Water Erosion • Moving water (like a stream) is an important agent in the erosion process. Dirt and other sediment get in the water and then the moving water moves it to a new location.   • Gravity plays an important role as well in erosion; gravity pulls down dirt and other stuff from the hills and causes erosion.

38. Wind Erosion • Wind erosion occurs mostly in flat, dry areas and close to bodies of water.  Wind erosion removes the most fertile part of soil and lowers the soil production. That means most crops and plants will not make it to harvest time. All that is left after wind erosion in soil is the clayish soil and silts.

39. In the 1930s a long dry spell got bad enough it turned into dust storms. They called it the Black Blizzards and it became known as  the Dust Bowls. • Want to know more? Click here

40. Weathering • Weathering is the process of decomposition or disintegration of rocks and their minerals. That is why it is considered a destructive force. The rocks and their minerals break down into smaller pieces like silt, clay and sand.

41. The weathering process occurs at or near the surface of the earth. In fact, the soil we depend on for much of our food is a mixture of bits and pieces of weathered rock.

42. Weathering and Water • One of the major causes of weathering is water. Moving waters such as rivers and oceans can permanently change the Earth's surface. The waters and rivers can carve deep canyons or weather cliffs along the seashore causing them to fall into the waters.

43. Rain water can also cause weathering. As it rains, rain water can seep into holes and cracks in rocks causing weathering and if this water freezes inside the rock, this can cause the rock to break into smaller pieces.

44. Extreme Heat • Extreme heat is an example of weathering that can cause destructive changes to the surface of the earth. • Rocks that become heated at the surface of the earth can expand and then contract. If this happens often enough the expansion and contraction of rock would eventually cause weathering.

45. Plants • Plant roots grow in cracks of rocks. As they grow, they force open the cracks. This is another way pieces of rock can be broken off.

46. Weathering and Erosion • Weathering and erosion often occur at the same time. After weathering has broken the rocks into smaller pieces, other processes like erosion and deposition move the broken pieces to other places. • Weathering is a destructive force because it changes rocks by breaking them into smaller pieces.

47. Weathering processes are divided into three categories: • ·  Physical or Mechanical Weathering • ·   Chemical Weathering • ·   Biological Weathering

48. Physical or Mechanical Weathering:   breaks larger rocks into smaller rocks without changing what the rock is made of. Examples • Chemical Weathering:   involves changing what the rock is made of. Chemical weathering causes the rocks to become weak and eventually crumble. Examples • Biological Weathering: is the actual molecular breakdown of minerals. • Example:Lichens live on rocks and they slowly eat away at the surface of rocks

49. Technology and Flood Control • http://www.gcwallace.com/ServicesLasVegasFloodControl.asp