Changes to the Earth’s surface

1. Changes to the Earth’s surface

2. The changing Earth • The surface of the Earth is always changing.

3. The Rock cycle • The rock cycle shows how rocks change back and forth between sedimentary, igneous, and metamorphic rocks.

4. The rock cycle - Igneous • Igneous rocks form when melted rock cools and solidifies. • The crystal size in an igneous rock is determined by how fast the rock cooled. • How fast the rock cooled is determined by how close to the surface the rock was, and how large the chamber was. • Igneous rocks can be extrusive or intrusive

5. The rock cycle - Igneous • Examples of igneous rocks include: • Obsidian • Granite • Basalt • Pumice • Rhyolite

6. The rock cycle – Sedimentary • Sedimentary rocks are formed by weathering, erosion, deposition, compaction, and cementation of other rocks.

7. The rock cycle – Sedimentary • Examples of sedimentary rocks include: • Sandstone • Limestone • Flint • Shale • Coal • Limestone

8. The rock cycle – metamorphic • Metamorphic rocks form when heat and pressure deep beneath earth’s surface cause one type of rock to change into another type of rock.

9. The rock cycle – metamorphic • Examples of metamorphic rocks include: • Gneiss (from Granite) • Quartzite (from Sandstone) • Schist • Slate (from Shale) • Marble (from Limestone)

10. Energy in the rock cycle • What types of energy are needed to form each type of rock? • Igneous • metamorphic • Sedimentary

11. Rock cycle • Heat energy is important in the formation of igneous and metamorphic rocks. • Where does that heat come from?

12. Heat energy • The earth gets hotter the deeper down you go, but why? • Radioactive decay

13. Kinetic energy • Some of the heat energy in the mantle is transformed into kinetic energy in the form of convection currents that form in the mantle.

14. Kinetic energy • Convection currents move the plates of the crust back and forth. • A place where 2 plates meet is called a fault.

15. Kinetic energy  Potential energy • Kinetic energy of the moving plates can be converted into potential energy when two plates collide and “stick” together. • The potential energy builds up until it is finally converted back into kinetic energy and the plates “slip”

16. Plate boundaries • Plates that pull apart are called divergent plates • Plates that push together are called convergent plates • Plates that slide past each other are called transform plates. • What do you think would happen to the earth at each type of boundary?

17. Plate movement • As plates slide over, under, or past each other, they change the surface of the earth.

18. Plate movement • Plates that push together can cause the earth to “crumple” and form mountains.

19. Plate movement • When continental and oceanic plates collide, they can produce volcanoes.

20. Plate movement • When plates “slip”, “smash” or “pull” apart they produce earthquakes. • During an earthquake, potential energy is converted to kinetic energy. • (Remember that this mechanical energy started as heat energy inside the earth.)

21. Plate movement • Some of the heat energy from the earth reaches the surface (as in a volcano.) • Some heat energy is transformed into mechanical energy in the form of convection currents, moving plates, earthquake waves, flowing lava, etc…

22. Energy  to infinity and beyond! • Earthquakes, volcanoes, and mountain formation all occur when the heat energy from inside the earth makes its way to the surface. (Either as heat energy or mechanical energy.)

23. Energy  to infinity and beyond! • Earthquakes and volcanoes can change earths surface very rapidly. • Mountains building is a slow and gradual process that changes earths surface. • These changes all occur because energy from earths interior transfers to the earth’s surface.

24. Changes to Earth’s surface • Some changes to the Earth’s surface are not caused by energy from the interior of the earth. • These changes can come from weathering, erosion, deposition, gravity, glaciers, and other “agents” of change.

25. Weathering • Weathering occurs when rock on the surface of the earth breaks down into smaller pieces. • Weathering can be mechanical or chemical.

26. Mechanical Weathering • Mechanical weathering is when mechanical energy creates weathering. This mechanical energy could come from: • Moving water/wind (abrasion) • Freezing ice • Burrowing animals • Growing plant roots

27. Chemical weathering • Chemical weathering occurs when chemical energy causes weathering to occur. • Things that could cause chemical weathering include: • Acid rain • Oxygen (oxidation) • Living things making acids to break down rock. (like lichens)

28. Erosion and deposition • Erosion occurs when water, wind, or ice move weathered rock particles from one place to another. • Deposition is when those particles being carried by erosion get laid down somewhere.

29. Weathering, erosion, and deposition • Weathering, erosion, and deposition are important parts in the process of soil formation.

30. Gravity • Gravity changes the surface of the earth. Particles that weather and erode in the mountains get carried to the valleys. • Gravity moves particles and sediment downhill.

31. Gravity • Gravity can cause several types of “mass movement” downhill including: • Landslide • Mudflow • Slump • Creep

32. Gravity – Mass movement • Landslides occur when rock and soil move quickly down a slope • Mudflows occur when water, rock, and soil move downhill. (Usually during heavy rain.)

33. Gravity – Mass movement • Slumps occur when an entire section of a hillside suddenly slides down a slope but stays together. • Creeps occur when rock and soil moves downhill very slowly.

34. Glaciers • Glaciers move slowly across the land. As they move, they shape the land in many ways.

35. Glaciers • Glaciers create features in the earth such as: • U-shaped valleys • Cirques • Horns • Drumlins

36. Weathering Erosion and Deposition • Weathering, erosion deposition and gravity can change the surface of the earth gradually or rapidly.

37. Rapid change • Flash floods, landslides, mudflows, earthquakes, volcanoes can all change the earth rapidly.

38. Gradual change • Mountain formation, mountain destruction, weathering, erosion, creep, and glacial activity are all gradual changes to earth’s surface.

39. Mountain building • The average mountain that is actively being built is moving upward at a rate of 6 mm/year and being eroded downward at a rate of 1 mm/year. • A mountain that takes 5 million years to build might take 100 million years to erode away.

40. Mountain building • As a mountain erodes away, the roots of the mountain push upward. • For every 5 mm of the mountain that erode away, the roots push up 4 mm. • The taller the mountain, the faster erosion occurs.