The Earth's Movement and Changing Seasons

1. Unit 2 Earth's Physical Geography

2. Our Planet, the Earth • How does the Earth move in space? • Why do seasons change?

3. The Earth and the Sun Days and Nights • The Earth travels around the sun in an oval-shaped orbit.

4. It takes 365 1/4 days, or one year, for the Earth to complete one revolution around the sun. • As the Earth revolves, it is also spinning on its axis. • Each rotation (or complete spin on the axis) takes about 24 hours. • It is daytime on the side facing the sun and night on the side away from the sun.

5. The Earth and the Sun Understanding Seasons Why are the days longer in some parts of the year? • The Earth’s axis is at an angle. • In about half of the Earth’s orbit, the tilt causes a region to face toward the sun for more hours than it faces away from the sun. • Days are longer. • In other regions that face away from the sun for more hours, days are shorter.

6. Why does the temperature change during the seasons? • The warmth you feel at any given time of year depends on how directly the sunlight falls on you. • Some regions receive a great deal of direct sunlight, while others receive very little. • This is also a result of the Earth’s tilt and orbit.

7. Spring and fall equinoxes: Days and nights are almost equal everywhere Equator March 21September 23 0º Tropic of Cancer 23 1/2º N June 21 First day of winter, or winter solstice, in Northern Hemisphere Tropic of Capricorn 23 1/2º S December 21 66 1/2º N Never Arctic Circle Antarctic Circle 66 1/2º S Never Looking at Latitudes Gets Direct Sunshine on Line of Latitude Where is it? Seasons

8. Zones of Latitudes

9. Looking at Latitudes: Zones • Low Latitudes: The Tropics • Area between the Tropic of Cancer and the Tropic of Capricorn • In this region, it is almost always hot.

10. Middle Latitudes: The Temperate Zones • Area between the Tropic of Cancer and the Arctic Circle • AND the area between the Tropic of Capricorn and the Antarctic Circle • In this region, there are seasons, each with a distinct pattern of daylight, temperature, and weather.

11. High Latitudes: The Polar Zones • Area between the Arctic Circle and the North Pole • AND the area between the Antarctic Circle and the South Pole • In this region it is very cool to bitterly cold.

12. Land, Air, and Water • What forces shape the land? • What are the Earth’s major landforms?

13. Forces Inside the Earth What is the Earth made of? The Earth’s surface is made up of 75 percent water and 25 percent land. Continents are unique, in part because of their landforms, which include mountains, hills, plateaus, and plains.

14. Pangaea: The Supercontinent • Geographers theorize that millions of years ago the Earth had only one huge landmass, which they call Pangaea.

15. They believe that 200 million years ago, some force made Pangaea split into several pieces and begin to move apart, forming separate continents.

16. The theory of plate tectonics explains why the continents separated. • Continents are part of plates that shift over time.

17. The Movement of the Continents When geographers first began to study world maps, they realized that the continents look like pieces of a jigsaw puzzle.

21. Volcanoes, Earthquakes, and Shifting Plates • The world’s plates move in different directions, causing a variety of effects: • Ridges: In some places, plates move apart, and magma leaks through the cracks in the crust. In the oceans, over time, the cooling rock builds up to form lines of underwater mountains called ridges.

22. Volcanoes: In other places, the plates push against one another, forcing one plate under the other. Tremendous pressure and heat builds up causing molten rock to explode on the surface.

23. Earthquakes: • Along plate boundaries, there are many weak places in the Earth’s crust. • When plates push against each other, the crust cracks and splinters from pressure. • These cracks are called faults. • When the crust moves along faults, it releases great amounts of energy in the form of earthquakes.

24. Forces on the Earth's Surface Forces like volcanoes slowly build up the Earth. Other forces slowly break it down. These forces may not be as dramatic, but they have important and long-lasting effects.

25. The Two Effects of Weathering: • Weathering breaks down rocks into tiny pieces, wearing away the Earth’s landforms. Many once-steep mountains are now low and rounded. Three things cause weathering: wind, rain, and ice. • Weathering helps create soil. Tiny pieces of rock combine with decayed animal and plant material to form soil.

26. Erosion • Once this breaking down has taken place, small pieces of rock may be carried to new places by erosion. Erosion, together with weathering, help slowly create new landforms.

27. Air and Water: Two Ingredients for Life Air • The thick layer of gases that surrounds the Earth is called the atmosphere. • It provides life-giving oxygen for people and animals and life-giving carbon dioxide for plants. • It also acts as a blanket, holding in enough heat from the sun to make life possible. • Winds distribute this heat around the globe.

28. Water • Roughly 97 percent of Earth’s water is found in the oceans. • The rest is fresh water, or water without salt. Most of that is frozen at the poles. • Fresh water comes from lakes, rivers, and rain. Much fresh water, called groundwater, is stored in the soil. • People need fresh water—the Earth has enough, but some places have too much, and others have too little.

29. The World: Wind Patterns

30. Climate and What Influences It • What is climate? • How do landforms and bodies of water affect climate?

31. Weather or Climate? Weather • What you check before you go outside in the morning • Day-to-day changes in the air • Measured primarily by temperature and precipitation

32. Climate • What you know from experience happens from year to year • The average weather over many years • The Earth has many climate regions. • Climates are different in low, middle, and high altitudes because latitude affects temperature. • Landforms, wind, and water also affect climates.

33. The Blowing Winds • Wind and water help spread the sun’s heat and keep the Earth from overheating. • Winds blow east–west and west–east in part because of Earth’s rotation.

34. Winds blow north–south and south–north because: • Hot air rises and circulates toward regions where the air is not as hot. • Hot, moist air from the Equator rises and moves toward the North Pole or South Pole. • Cold air sinks and moves toward regions where the air is warmer. • Cold, dry air from the poles moves toward the Equator.

35. Ocean Currents: Hot and Cold The Earth’s rotation creates ocean currents. Warm water from the Equator flows north or south to colder parts and cold water from the poles flows toward the warm areas near the Equator.

36. The Ocean's Cooling and Warming Effects Bodies of water affect climate in another way too: Why is a beach on a hot summer day cooler by the ocean? • Water takes longer to heat or cool than land. • In the summer, a place near the ocean or a lake will be cooler than an area farther away.

37. The water currents are colder than the air, so the current absorbs heat, making the temperature fall. • In the winter, that area will be warmer. • The water currents are warmer than the air, so the current gives off its warmth and the air temperature rises.

38. Raging Storms Wind and water can make climates milder, but they also can create storms. Some storms create great destruction.

39. Hurricanes • Wind and rain storms that form in the tropics in the Atlantic Ocean • The winds at the center travel over 73 miles per hour. • They produce huge waves called storm surges, which flood over shorelines and can destroy homes and towns.

40. Typhoons • Similar to hurricanes, they take place in the Pacific Ocean.

41. Tornadoes • Swirling funnels of wind that can reach 200 miles per hour. • The powerful winds can wreck almost anything in a tornado’s path. • However, they only average about one half mile in diameter. • Therefore they affect a more limited area than hurricanes.

42. How Climate Affects Vegetation • Where are the Earth’s major climate regions? • What kinds of vegetation grow in each climate region?

43. Climate and Vegetation • Plants have features, called adaptations, that enable them to live in a particular climate. • Over a very long time, small, accidental changes in a few individual plants made them better able to survive in a particular place. • Therefore, geographers can predict the kinds of plants they will find in a climate. • Each climate has its unique vegetation, or plants that grow there naturally.

44. Geographers discuss five broad types of climates: • Tropical • Dry • Moderate • Continental • Polar

45. Types Tropical Wet Tropical Wet and Dry Arid Semiarid Temperature Hot Hot Moisture Wet Dry Vegetation Tropical rain forest: Because there is so much light, heat, and rain, thousands of kinds of plants grow here. The uppermost branches of tall trees create a canopy, and plants more adapted to shade grow beneath. Sparse: Because there is so little rain, plants grow far apart and have shallow roots adapted to absorb scarce water before it evaporates. Some plants flower only when it rains. Tropical and Dry Climates Tropical Climates Dry Climates

46. Types Mediterranean, Marine West Coast, Humid Subtropical Temperature Seasonal, but almost never below freezing Moisture Moderate rain Vegetation In General: A wide variety—forests of deciduous trees, tall shrubs, low bushes, a variety of grasses Humid Subtropical: Has the most heat and precipitation and many types of vegetation Marine West Coast: Mountainous and cooled by ocean currents—supports more forests than grasses Mediterranean: Rainy winters and hot, dry summers lead to plants with leathery leaves, which hold in moisture during the dry summers. Moderate Climates Moderate Climates

47. A Vertical Climate • A mountain is an example of a vertical climate, where the climate changes according to the mountain’s height. • A hike up a tall mountain in a moderate climate would go something like this: • Grasslands surround the base, and temperatures are warm.

48. You soon enter a region with less precipitation than below—there are short grasses, as in a continental climate.

49. Next, you move through deciduous forests where it is cooler and drier. • Slowly the forests change to coniferous forests.

50. Then, you find only scattered, short trees and finally only low shrubs and short grasses. • Soon it is too cold and dry even for them and you begin to see mosses and lichens of a tundra.