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Constructive & Destructive Forces

Constructive & Destructive Forces. EQ: What is the difference between a Constructive Force and a Destructive Force?. Constructive Forces- Natural forces that build or construct landforms and cause changes in the Earth’s surface. Examples: Volcanoes Deposition Earthquakes.

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Constructive & Destructive Forces

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  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 • Deposition • Earthquakes

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

  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. http://jclahr.com/alaska/aeic/taurho/eqeffects/eqtsun.mov

  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. 3 Types of Stress: • Shearing – Pushes rock in opposite directions past each other - Transform boundaries

  10. 3 Types of Stress: • Tension – Stretches rock so that it becomes thinner in the middle - Diverging boundaries

  11. 3 Types of Stress: • Compression – Squeezes rock until it folds or breaks - Converging boundaries

  12. 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

  13. 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)

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

  15. 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

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

  17. Best Way to Protect Yourself: DROP!! COVER!! HOLD!!

  18. 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.

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

  20. Pahoehoe Aa

  21. 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

  22. 2 Types of Weathering: • Mechanical • Chemical

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

  24. 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.

  25. Rock split apart by Mechanical weathering.

  26. 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

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

  28. Chemical Weathering: • Caused by…(Agents) • H2O(Water)  MOST important • Oxygen (O2) • Carbon Dioxide (CO2) • Living organisms • Acid Rain  very rapid

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

  30. 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

  31. 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

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

  33. Mudslide

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