1. Constructive & Destructive Forces

2. EQ: What is the difference between a Constructive Force and a Destructive Force?

3. Constructive Forces- Natural forces that build or construct landforms and cause changes in the Earth’s surface.
Examples:
Volcanoes -Delta
Deposition -Faults
Earthquakes -Sand Dunes

4. Constructive Forces
Constructive forces affect the earth's surface by building it up to form new landforms like mountains and islands.
Examples of these type of forces are:
Deposition is the dropping off of bits of eroded rock. This process helps to build up Earth’s surface by filling in depressions, or basins.
Earthquakes
Volcanoes

5. - Earthquakes - Glaciers
Destructive Forces – Natural forces that destroy landforms and causes damaging changes in the Earth’s surface.
- Earthquakes Glaciers
Weathering/Erosion - Landslides
Volcanoes - Tsunami

6. Earthquakes:
Shaking that results from the movement of rock (tectonic plates) beneath Earth’s surface
Destructive force or Constructive force
Most occur because of moving crust

7. Earthquakes causes vibration across the ground, sending shock waves that crumble buildings.

8. Stress: Force that acts on rock to change its shape and volume
Energy is stored in the rock until it breaks or changes shape

9. Faults:
Break in Earth’s crust where slabs of crust slip past each other
When stress builds up, the rock breaks along a fault
Usually occur along plate boundaries

10. 3 Main Types of Faults:
Strike-Slip – Rocks on each side slide past each other with little (or no) up & down motion
- Transform boundaries
- Caused by Shearing
- San Andreas (California)

15. Measuring Quakes: Seismograph –
instrument used to measure the vibrations and seismic waves of earthquakes.

16. Rating Scales used for Quakes:
Richter – Rate quakes according to the size of the seismic waves
- low ---> high (1-9)
-each # is 10x stronger
- humans cannot feel a quake below 2
- 6 or more = major quake
- Measures magnitude

18. Misc. Info: Tsunami – a series of seismic sea waves
- result from underwater earthquakes, landslides, or volcanic eruptions

19. Volcanoes: Destructive AND Constructive
Weak spot in the crust where molten material from the mantle comes to the surface
Magma – Hot molten rock located Below ground.
Lava – magma that reaches the surface.

20. Volcanoes can quickly change the Earth, too, by pouring out hot, liquid rock called lava.

21. Pahoehoe Aa

24. Weathering:
Process that breaks down rock & other substances at the Earth’s surface- very slow process
Temperature, Water, & gases in the atmosphere all contribute to weathering

25. 2 Types of Weathering:
Mechanical
Chemical

26. Mechanical Weathering:
Process by which rock is physically broken into smaller pieces
Small pieces have same material as the original rock
Very slow occurrence

27. The most common type of mechanical weathering is the constant freezing, and thawing of water. In liquid form, water is able to penetrate the many holes and joints within a rock. As the temperature drops water freezes and expands, becoming about 10% larger than it was in liquid form. The result is that the holes and cracks in rocks are pushed outward. Even the strongest rocks are no match for this force.

28. Rock split apart by Mechanical weathering.

31. Mechanical Weathering:
Caused by…(Agents)
Freezing and Thawing
Release of Pressure
Growth of Plants
Abrasion – Grinding away of rock by other rock particles that are carried by water, ice, wind, or gravity

32. Chemical Weathering:
Breaks down rock through chemical changes- Chemical properties are actually changed.
Rock particles have different mineral make-up than original rock

33. Stalactites & Stalagmites created by acid rain falling into these limestone caverns.

36. Erosion:
Process by which natural forces move weathered rock & soil from one place to another (by wind, water, ice, & gravity)
Sediment
Material moved by weathering and erosion

37. Mass Movement: Deposition Caused by gravity
Occurs where bits of rock are dropped off (deposited) because of erosion
On land sediment can be moved down hill by:
Landslide
Mudslide

38. Landslide: Most destructive
When rock & soil slide quickly down a steep slope

39. Mudslide

40. Technology and Human Interventions
Humans try to CONTROL these forces.
seismological studies
flood control (dams, levees, storm drain management, etc.)
beach reclamation (Georgia coastal islands)

41. Seismological Studies
Scientists study earthquakes so that they can understand how they work and so that they can try to predict future quakes.
Earthquakes are recorded by instruments called “seismographs”.
A short wiggly line means a small earthquake and a large one means a large earthquake.

43. Flood Control
The U.S. Army Corps of Engineers began constructing dams in Georgia for navigation and flood control in the 1940s and 1950s under the Flood Control Act of 1944 and the Watershed Protection and Flood Prevention Act of 1954.

44. Flood Control Methods
Dams control the water flow in a stream or river.
A levee is an embankment designed to prevent the flooding of a river.
Storm drains are for carrying off rainfall drained from paved surfaces, roofs, etc.

45. Beach Reclamation
Weather, waves and wind cause the coastline to wash away.
Keeping sand dunes intact helps to keep the beaches from eroding.