Read Across America. Listen as I read for facts about Volcanoes. In the Shadow of the Volcano

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Ashley Booth
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1 Read Across America Listen as I read for facts about Volcanoes. In the Shadow of the Volcano

2 Constructive & Destructive Processes

3 Earth s surface is always changing. Blowing wind and flowing water causes some changes. Moving rock deep inside Earth causes other changes. These processes wear Earth s surface down in some places and build it up in others.

4 Changes over Time: Destructive Processes Destructive Processes: wear Earth s surface down. Constructive Processes: build Earth s surface up.

5 Weathering -the breaking down of rock at or near Earth s surface. o Wind and water can carry sand and other small pieces of rock. o Sand and pebbles carried by moving water also weather rock. On rocky coast, ocean waves break down rock cliffs in this way.

6 o Rain causes weathering- rainwater can seep into cracks in rock and in the winter the water may freeze. It then expands, or takes up more space. The ice in the cracks pushes against rock. Over time, repeated freezing and thawing of water may split the rock apart. This is called ice wedging.

7 Ice Wedging

8 o Plants causes weathering. The roots can grow into cracks in rocks. As the roots become larger, they push on the rock and may break it apart.

9 owind, water and sometimes plants work together to weather rock. Over long periods of time, weathering breaks rocks into smaller and smaller pieces. Small pieces include pebbles, sand and smaller rock. Small pieces of rock, along with material from living things, make up soil. Soil is the material in which most plants grow.

10 Soil is basically the accumulation of weathering products and organic matter along the surface of the earth between the atmosphere and bedrock

11 those rocks have been weathered and eroded over many, many years to cause them to have small pieces broken off the original rock until it is smoothed down. Weathering Brain Pop Video

13 Erosion: the process by which weathered rock is picked up and moved. owind picks up sand and moves it. Strong winds can bounce and roll larger pieces of weathered rock along the ground.

14 Wind Erosion

15 Wind Erosion

16 Wind Erosion

17 o Flowing rivers pick up soil, sand, and pebbles from the riverbanks and river bottoms. Rivers may carry this material over long distances. Over time, river valleys form. In some cases, rivers cut deep canyons.

18 The Colorado River carved out the Grand Canyon over millions of years.

19 Ocean waves too, pick up and move sand and other pieces of weathered rock.

20 Wave cut platform caused by erosion of cliffs by the sea

21 o Glaciers: huge sheets of ice that move slowly over land. As they scrape over Earth s surface, they erode rock and soil. Can pick up boulders the size of cars. Can form in narrow valleys. As they move, they widen and deepen these valleys. Can also scoop out holes in the ground. These holes can later fill with water to form lakes.

25 Erosion would not happen without gravity. Gravity is the force that pulls all objects toward each other. On Earth, gravity pulls everything down toward the center of the planet. Gravity makes water flow and winds blow. Sometimes gravity causes erosion directly, by pulling pieces of rock downhill. The sudden movement of rocks and soil down the side of a hill is called a landslide.

26 Landslide

27 Landslide

28 o The activities of animals can speed up erosion. Animals such as rabbits and moles dig burrows and tunnels in the ground. Then rain can wash the soil away more easily. o Humans clear land to build cities, towns, and roads. o Erosion Brain Pop Video

30 Earthquakes o Some destructive processes start deep inside Earth. o Pressure builds up in rock far below the surface, the pressure becomes so great that rock breaks and moves suddenly. The ground shakes. This shaking of the ground is an Earthquake. Wide cracks may open in the ground. Strong earthquakes can destroy buildings, roads, and bridges

Volcanoes o is an opening in Earth s surface that lets hot, melted rock and gases escape. o A sudden escape of these materials is called an eruption.

33 Volcanoes o is an opening in Earth s surface that lets hot, melted rock and gases escape. o A sudden escape of these materials is called an eruption. An eruption can blow the top off a volcanic mountain. Melted rock flows out, and ash settles on the ground. Trees, plants and animals die. Earthquakes and volcanoes are destructive, but they can also build landforms.

35 Changes over Time: Constructive Processes

36 Deposition Weathering breaks down rock into smaller pieces erosion moves pieces of rock to new places Wind and water move the rock pieces along, but when wind and moving water slow down, they cannot carry as much material They drop some or all of the rock pieces they are carrying.

37 Deposition is the dropping of material by water, wind, or glaciers. The deposition material is called sediment, which builds up into new landforms. Observe how sediment is transported by flowing water.

39 Deltas a flat piece of land made up of sediment deposited by a river near its mouth. - is usually shaped like a triangle or fan.

41 Delta building into lake.

42 Floodplains Heavy rainfall, a river may overflow its banks. Then water spreads out over the land on both sides of the river. The water slows down and drops the sediment it is carrying. The sediment forms a wide, flat area of land called a floodplain.

43 watch clip of floodplain

44 The erosion of the outside edge of the stream's banks begins the work of carving a floodplain, which is a flat level area surrounding the stream channel.

45 Beaches Ocean water deposits sediment. - the sand on beaches starts far inland. Rivers carry it to the ocean, where it sinks to the bottom. Ocean waves wash some sand back on shore. Over thousands of years a beach forms.

46 The swash throws sediments onto the beach. As the backwash is less powerful, only finer pieces are brought back to the sea.

47 Dunes - a hill of sand deposited by wind that form along some ocean shores and in sandy deserts. Wind blowing from the ocean toward land picks up sand along the shore and deposits it nearby. As the wind deposits more sand, dunes form.

48 The formation of dunes.

50 Moraines - a ridge of rock and soil deposited when a glacier melts. As a glacier moves it picks up rock and soil and then when it melts it leaves

52 Earthquakes can build up areas on land. They happen when rock suddenly moves along a fault. A fault is a break in the rock that makes up Earth s crust, or top layer.

53 Pressure deep underground may push the land on one side of the fault upward. The result is a clifflike landform called a fault scarp.

Over millions of years, rock pushed up along faults can

56 Changes during an earthquake happen quickly, but rock can also move at faults much more slowly. Over millions of years, rock pushed up along faults can form tall mountain ranges. The Sierra Nevada Mountains in California formed in that way.

Volcanoes Volcanic eruptions also build up Earth s surface. When a volcano erupts, hot, melted rock flows out of it. Melted rock underground is called magma.

57 Volcanoes Volcanic eruptions also build up Earth s surface. When a volcano erupts, hot, melted rock flows out of it. Melted rock underground is called magma. When magma reaches the surface it is called lava. On the surface, lava cools and hardens and forms solid rock. As a volcano erupts over and over, rock formed from lava piles up. Over a long time, a mountain can form.

59 The Hawaiian Islands are mountains that formed around volcanoes on the ocean floor. Lava flowing from the volcanoes built up the mountains until they stuck out of the water. Some of the Hawaiian Islands are still becoming larger, as the volcanoes continue to erupt. Volcanoes Brain Pop Video

62 Vocabulary Words to Know 1. Deposition- the dropping of material by water, wind or glaciers. 2. Sediment- rock particles or other material deposited by water, wind, or glaciers. 3. Delta- a flat piece of land made up of sediment deposited by a river near its mouth. 4. Floodplain- a wide, flat area of land formed from sediment deposited by a river outside its bank

63 5. Dune- a hill of sand deposited by wind. 6. Moraine- a ridge of rock and soil deposited when a glacier melts. 7. Fault- a break in the rock that makes up Earth s crust, or top layer. 8. Magma- melted rock below Earth s surface. 9. Lava- melted rock that has reached Earth s surface.

Changes over Time: Destructive Processes

1 Name Date Changes over Time: Destructive Processes Earth s surface is always changing. Blowing wind and flowing water causes some changes. Moving rock deep inside Earth causes other changes. These processes