Chapter 2 The Physical World

1. Chapter 2The Physical World

2. Section 1Planet Earth

3. Our Solar System • The sun and the objects that revolve around it including the Earth • Sun’s mass creates gravity which keeps the objects revolving around it

4. Planets • Spherical objects orbiting the sun • Inner planets: Mercury, Venus, Earth & Mars • Outer planets: Jupiter, Saturn, Uranus & Neptune

5. Dwarf planets • Small round bodies that orbit the sun but have not cleared the area around their orbits of other orbiting bodies • Ex: Pluto & Ceres

6. 2 types • Terrestrial planets – have solid, rocky crusts; Mercury, Venus, Earth & Mars • Gas giant planets – more gaseous & less dense; larger in diameter; Jupiter, Saturn, Uranus, & Neptune

7. Asteroids • Small, irregularly shaped, planet-like objects found mainly between Mars and Jupiter in the asteroid belt

8. Comets • Icy dust particles & frozen gases • Orbits are inclined to Earth’s orbit from any direction

9. Meteoroids • Pieces of space debris (rock & iron) • Usually burn up when reach the Earth’s surface

10. Earth • Rounded object wider around the center than from top to bottom • Diameter = 7,930 miles at the Equator • Circumference = 24,900 miles

11. Earth’s surface • 70% water – hydrosphere: oceans, lakes, rivers & other bodies of water • 30% land – lithosphere: islands, continents & ocean basins

12. Other spheres • Atmosphere – layer of gases extending above the Earth’s surface; air we breathe; 78% nitrogen, 21% oxygen • Biosphere – part of Earth that supports life

13. Section 2Forces of Change

14. Layers of Earth • Core – super-hot, solid inner layer of the planet surrounded by a band of melted iron & nickel (liquid outer core)

15. 2. Mantle – thick layer of hot, dense rock consisting of silicon, aluminum, iron, magnesium, oxygen & other elements; continually rises, cools, sinks, warms up & rises again releasing 80% of generated heat

16. 3. Crust – outer layer of the Earth’s surface; thin layer of rock (2-75 miles thick); broken into great slabs known as plates which float on a partially melted layer in the upper portion of the mantle & carry the oceans and continents

17. Pangaea • Supercontinent of Earth’s landmasses that broke apart into the smaller continents in existence today

18. Continental drift • Theory that continents were once joined and slowly drifted apart

19. Plate tectonics • The physical processes that create the earth’s physical features • May have created oceans & mountain ranges as well as the continents

20. Mountains • Created where giant continental plates collide (Himalaya Mtns) or when a sea plate collides with a continental plate through a process known as subduction (Andes Mtns)

21. Subduction • Process in which a heavier sea plate dives beneath the lighter continental plate and becomes molten material which then bursts through the crust to form volcanic mountains

22. Accretion • Pieces of the Earth’s crust come together slowly as the sea plate slides under the continental plate leveling off seamounts (underwater mountains) and piling up debris in trenches • Causes continents to expand

23. Folds • Bends in the layers of rock created as moving plates squeeze the Earth’s surface and it buckles

24. Faults • Cracks created in the Earth’s surface as plates grind or slide past each other • San Andreas Fault in California

25. Earthquakes • Sudden, violent movements of tectonic plates along a fault line • May change the surface of the land and the floor of the ocean

26. Ring of Fire • Zone of earthquake and volcanic activity around the perimeter of the Pacific Ocean

27. Volcanoes • Mountains formed by lava or by magma that breaks through the Earth’s crust often rising along plate boundaries where one plate plunges beneath another

28. Weathering • Chemical or physical processes, such as freezing, that break down rocks

29. Physical weathering • Occurs when large masses of rock are physically broken down into smaller pieces • Ex: water seeps into the cracks of a rock, freezes, expands and causes the rock to split

30. Chemical weathering • Changes the chemical makeup of rocks • Ex: rainwater containing carbon dioxide dissolving rocks such as limestone

31. Wind erosion • Involves the movement of dust, sand, and soil from one place to another

32. Glacial erosion • Large bodies of ice moving across the Earth’s surface picking up rocks and soil, changing the landscape

33. Moraines • Large piles of rock and debris left behind as glaciers melt and recede

34. 2 types of glaciers • Sheet glaciers – flat, broad sheets of ice which advance a few feet each winter and recede in the summer (cover most of Greenland & Antarctica)

35. 2. Mountain glaciers – located in high mountain valleys with a cold climate

36. Water erosion • Occurs when springwater and rainwater flow downhill, cutting the land and wearing away the soil and rock forming first gullies and then canyons

37. Soil • Product of weathering and biological activity • 5 factors: 1. Climate (wind, temperature, & rainfall) 2. Topography (shape & position of Earth’s physical features)

38. 3. Geology (determining the original rock material influences depth, texture, drainage, & nutrient content) 4. Biology (living & dead plants and animals add organic matter) 5. Time (of other factors)

39. Section 3Earth’s Water

40. Water cycle • Regular movement of water on the Earth • Evaporation – changing of liquid water into vapor (gas) caused by the sun’s energy

41. Condensation – process of excess water vapor changing into liquid water when warm air cools • Precipitation – rain, snow or sleet which falls to the Earth when clouds gather more water than they can hold; sinks into the ground, collects in streams & lakes to return to the oceans

42. Oceans • 5 divisions of the water circling the Earth • Pacific, Atlantic, Indian, Arctic and Southern (extends from the coast of Antarctica north to 60º S latitude)

43. Desalination • Process of turning saltwater into freshwater

44. Freshwater • 3% of the Earth’s total water supply • Very little is actually available for human consumption

45. Groundwater • Freshwater that lies beneath the Earth’s surface and comes from rain and melted snow • Source for wells and springs

46. Aquifer • Underground porous rock layer saturated by very slow flows of water