1. Changes to Earth’s Surface

2.  The surface of the Earth is constantly changing. Some changes happen quickly and can be dangerous. Others happen so slowly, you would have to live for thousands of years to notice even a small difference.

3. Slow Changes: Weathering  Weathering is the breakdown of rocks into sediments and minerals  Minerals are nonliving, solid materials that are formed in nature and made of crystals. Rocks are made of different types of minerals. Rocks Minerals

4. Slow Changes: Weathering  Weathering is caused by different physical forces.  Water and ice  Plants and animals  Chemical reactions  Built up pressure  Weathering produces sediments, or small pieces that break off of rocks.  Examples of sediments are pebbles, sand, silt, and mud.

8. Slow Changes: Erosion  Erosion is the movement of sediment by wind, water, ice, or gravity.  Runoff, creeks, streams, and rivers pick up and carry sediment away. This can weather the landscape in dramatic ways.

9. Slow Changes: Erosion  The overuse of land by humans can have an impact on the Earth’s surface. When humans clear land, the bare soil erodes easily.

10. Slow Changes: Erosion  Glaciers are gigantic formations of ice that do not completely melt over the course of a year. Glaciers can erode rock, grind mountains into valleys, and carve out lakes.

11. Slow Changes: Erosion  When sediments land somewhere else and stay for a while, it is called deposition. Lots of sediment is deposited at the mouth of a river. A growing pile of deposited sediment at the mouth of a river is called a delta. The Nile River Delta

12. Bill Nye: Erosion  http://www.youtube.com/watch?v=D7WFeh30U pY http://www.youtube.com/watch?v=D7WFeh30U pY

13. Rapid Changes to Earth’s Surface  Some changes to the Earth’s surface happen rapidly, such as fires, floods, earthquakes, volcanoes, and tornadoes.  Earth’s crust is like a jigsaw puzzle, made up of large and small sections called tectonic plates. Energy from the Earth’s core and mantle pushes them around so they are in constant, slow motion. The plates can cause earthquakes and volcanoes.

14.  http://www.ucmp.berkeley.edu/geology/anim1.html http://www.ucmp.berkeley.edu/geology/anim1.html

15. Rapid Changes: Earthquakes  Earthquakes are caused by the movement of the Earth’s plates. When the plates move, they grind against each other. Earthquakes occur at points where the plates get stuck. Tension builds, and then the plates move quickly.  http://earthquake.usgs.gov/earthquakes/map/ http://earthquake.usgs.gov/earthquakes/map/  http://www.weatherwizkids.com/weather-earthquake.htm http://www.weatherwizkids.com/weather-earthquake.htm

16. Rapid Changes: Volcanoes  Volcanoes are often found along the edges of the plates. Far beneath the Earth’s surface, high temperatures cause rock to turn into liquid. The liquid rock is called magma. Magma escapes from the center of the Earth through volcanoes. The magma is then called lava.

17. Rapid Changes: Flooding  Large amounts of rain can cause flooding. Flooding can damage natural areas and man- made structures. However, flooding can sometimes have a positive effect on soil.

18. Rapid Changes: Drought  When an area does not get enough rain for an extended period of time, it experiences a drought. As a result of this water shortage, many plants and animals die.

19. Rapid Changes: Fires  When the land is too dry, forest and grass fires are easily started. Many of the fires in nature are caused by humans, but some are caused by lightning. Fires can destroy animal habitats, decrease water supply, and leave the land open to erosion.  However, fires can be helpful to plant growth. Fire gets rid of the dead underbrush, clearing the land for new plant growth.

20. Studying Environmental Changes:  The greenhouse effect causes a gradual increase of temperature around the world. This increase is known as global warming. The temperature melts ice caps, causing the sea level to rise. When the sea level rises, flooding can occur along the coasts.  Video: http://www.epa.gov/climatestudents/basics/today/g reenhouse-effect.html http://www.epa.gov/climatestudents/basics/today/g reenhouse-effect.html

21. Studying Environmental Changes:  Scientists use different types of evidence to learn about how the environment has changed  When a tree is cut, you can see growth rings. The tree rings tell you how old the tree is. Wider rings indicate a warm wet season, and thinner rings indicate dry seasons.

22. Studying Environmental Changes:  When sediments cover dead plants or animals, fossils can form. Fossils are the remains or traces of animals and plants that lived long ago. Fossils allow people to study organisms that have been extinct for thousands or millions of years. Scientists date the fossils by where they were found in the layers of rock. The bottom layers of rock are older than the top layers.

23. Rock Layers of the Grand Canyon

24. Studying Environmental Changes:  Ice cores can be used to learn about changes in the climate of ice regions. Long, narrow pieces of ice are drilled from the ground and removed. Bands of light and dark snow can be seen. The older snow is at the bottom, and the newer snow is on top. Air bubbles from hundreds of years ago are trapped in the layers.