Chapter 1, Section 3. I. Changes on the Earth’s Surface A.Weathering i.Is the breakdown of rock at or near the earth’s surface into smaller and smaller.

Chapter 1, Section 3

I. Changes on the Earth’s SurfaceA. Weathering

i. Is the breakdown of rock at or near the earth’s surface into smaller and smaller pieces.

ii. Two types of weathering.a. Mechanicalb. Chemical

a. Mechanical Weathering1. Occurs when rock is actually broken or

weakened physically. 2. Breaks large masses of rock into smaller

pieces, producing boulders, stones, pebbles, sand, silt and dust.

3. Most common type of Mechanical Weathering is known as Frost Wedging.

b. Chemical Weathering1. Alters a rock’s chemical makeup by changing

the minerals that form the rock or combining them with new chemical elements. – This means chemical weathering can change one

type of rock into an entirely different type causing the loss of valuable minerals (leaching).

– Most important factors water and carbon dioxide.

*** Acid Rain is another type of chemical weathering. Some known causes of acid rain are acid-producing agents from the ocean, volcanic activity and industrial pollution.

c. Observing Weathering

1. Besides the effects on old stone structures such as tombstones, it also softens the sharp features on carved stone statues, and breaks down the mortar that holds together stone or brick walls.

2. Weathering also changes natural landforms, jagged mountains can turn to rounded hills over millions of years.

B. Erosion1. The movement of weathered materials such

as gravel, soil and sand. 2. The three most common causes of erosion

are a. water, b. wind and c. glaciers.

a. Wateri. Moving water – rain, rivers, streams and

oceans – (mixed with sediments AKA small particles of soil, sand and gravel) is the greatest cause of erosion.

b. Windi. Caused the “Dust Bowl” during the 1930s.ii. Drought caused soil to dry, wind blew and

stripped the land of its minerals and nutrients.

iii. Sandstorms are major causes of erosion.

c. Glaciersi. Huge, slow-moving sheets of ice. ii. While rivers cut sharp-sided, V-shaped

valleys, glaciers carve out valleys that are rounded and U-shaped.