Key Vocabulary Terms

weathering - breaking down of rocks on the earth's surface
mechanical weathering - breaking apart of rocks without dhanging their mineral composition.
chemical weathering - breaking apart of rocks caused by a change in their chemical makeup
oxidation - process in which minerals combine with oxygen to form new substances.
soil mixture of tiny pieces of weathered rock and the remains of plants and animals.
topsoil - top layer of soil, rich with oxygen and decayed organic matter.
subsoil - layer of soil directly below the topsoil.

Key Concepts

Weathering is caused by air, water, and living things.
Mechanical weathering is may be a plant browing in a small crack of rock; as the plant grows, its roots split the rock. Or water may freeze in the cracks of rocks. As the freezing water expands, it pushes the rock apart. After the water melts and refreezes several times, the rock breaks apart.
A limestone cave forms when rain and groundwater combine with carbon dioxide in the air. the resulting carbonic acid dissoves calscite in limestone, eventually changing small holes into huge caves.
Topsoil is the layer of soil that contains the most decayed material.
Solid rock lies below three layers of soil.

Did you learn these Objectives?

Are you able to define weathering?
Can you give examples of mechanical and chemical wathering?
Are you able to identify different soil layers?

Investigation 12-1 "Observing Chemical Weathering" (Optional, must complete 16 total investigations)

Key Concepts

You will model and observe chemical weathering by exposing limeston to acid.

Lesson 2 "Erosion Caused by Water"

Key Vocabulary Terms

erosion - wearing away and moving of weathered rock and soil.
meander - looping curve in a river.
floodplain - low, flat area that a river covers when it overflows its banks.
oxbow lake - C-shapted body of water formed whn a meander is cut off from the rest of the river.
deposition - dropping of eroded sediment.
mouth - place where a river flows into a larger body of water.
delta - fan-shaped area of land formed when sediment is deposited where a river empties into a lake or an ocean.
alluvial fan - fan-shaped area of land deposited wehre a mountain stream moves onto flat land.

Key Concepts

Erosion is the wearting away and moving of weathered rock and soil.
a young river is narrow and fast, can move boulders, and occupies most of its V-shaped valley. It may contain rocky ledges, waterfalls, and rapids. An old river slowly moves across a flat, witde valley that has eroded to near sea level. It meanders across a floodplin, can move only small sediment, and may have created oxbow lakes over time. Its valley is much wider that the river itself.
As a meander continues to grow, it forms a more pronounced loop, almost a circle. During a flood, the river may brak through its banks and flow straighter, cutting off the meander and forming an oxbow lake.
A delta is formed by sediment building up at the mouth of a river. An alluvial fan forms similarly, but at the base of a mountain where a mountain stream meets flat land.
Sand on a beach comes from erode rocks along the shore and from rivers that flow over rocks as they make their way to the lake or ocean.

Did you learn these Objectives?

Can you explain how rivers erode the land?
Are you able to describe how river valleys form and age?
Can you explain deposition and delta formation?
Are you able to identify shoreline features caused by waves?

Investigation 12-2"Comparing Erosion" (Optional, must complete 16 total investigations)

Key Concepts

You will find out if vegetation affects erosion and answer the question, do the trees, shrubs, and plans growing on a hillside help prevent erosion?

Lesson 3"Erosion Caused by Glaciers"

Key Vocabulary Terms

glacier - thick mass of ice that covers a large area.
cirque - bowl-like basin in a mountain that is carved out by an alpine glacier.
horn - jagged, pyramid-shped peak formed by the intersetion of three or more cirques.
moraine- ridge of sediment deposited by a glacier.

Key Concepts

Alpine glaciers form in mountain valleys. Continental glaciers are much bigger and cover large areas of land.
A glacier erodes land as it moves because the mass of moving ice and scraping action of the rocks embedded near the bottome of the blacier cause erosion of the land as the glacier moves and drops soil and rocks.
A horn forms when several cirques around the top of a mountain form a pyramid-shaed peak.
A moraine forms when glacier ice melts and deposits sediment, forming ridges.
The great Lakes formed when continental glaciers carved wide, deep basins. When they melted, the water filled the basins, forming the Great Lakes.

Did you learn these Objectives?

Are you able to define two types of glaciers?
Can you explain how glaciers erode the land?
Are you able to describe features caused by glaciers?

Lesson 4 "Erosion Caused by Wind and Gravity"

Key Concepts

Wind erodes land by blowing particles against rocks and by transporting particles to other places.
A sand dune forms when wind causes sand to pile up behind an obstacle. As the sand accumulates, it blocks more sand and eventually a large dune is formed.
Sand dunes form in deserts and around beaches.
Erosion caused by gravity include mudflows, landslides, falling rocks, and tilted objects.
Rocks and soil are looseded by freezing and thawing and by heavy rains.

Did you learn these Objectives?

Are you able to describe how wind erodes land?
Can you explain how sand dunes form?
Can you identify examples of erosion by gravity?

Chapter Summary and Review

See pages 304-305.

Chapter 12 Review answers are

1. erosion

2.delta

3. weathering

4. meander

5. horn

6. soil

7. alpine

8. moraine

9. oxbow lake

10. cirque

11. B

12. D

13. A

14. C

15. C

16. D

17. A. topsoil; B subsoil; C weathered rock; D solid rock

18. Plowed tracks across a hillside would be level, helping prevent soil erosion when water runs down the slope. Plowed tracks down a hillside would be sloped like the hill, increasing soil erosion by water and gravity.

19. as a rock breaks into smaller pieces. more of it is exposed to air, water, and living things, factors that promote more weathering.

20. You might suggest that barricades be built around the dune to prevent their blowing into the neighborhood. A better solution would be to grow plants on the dunes, as vegetation would anchor the sand and keep it from beting blown away.