Soil Formation Study Questions

1. Soil is made up of rock particles (clay, silt, sand, and gravel), minerals, air, water, and organic matter (decayed organic material is called humus).

2. Loam is fertile, good for growing plants. The humus in loam provides nutrients and spaces for air and water--loam is about 25% air and 25% water. Also loam is about equal parts clay, sand, an silt, so the texture of the soil holds in a good amount of water. (Too much clay means too much water and too much sand means it doesn't hold in enough water.)

3. The soil horizons form in the order C, then A, then B. First bedrock is weathered to produce the C horizon (partially weathered rock). Then the C horizon is weathered and plants grow and contribute their parts to the soil which creates the A horizon (topsoil). Then particles from the A horizon (mostly clay and other rock particles) wash down and mix with the C horizon to make the B horizon (subsoil).

4. Humus is dark colored organic matter (made from plants and animals) that is found mostly in the topsoil. When remains of plants and animals decay due to activity of decomposes (like earthworms or bacteria) then humus is formed.r

5. Soil is mixed by organisms in the soil. Burrowing animals and earth worms can mix the soil.

Rocks and Weathering Study Questions

1. Weathering breaks down rock into small particles, or sediment. Forces of erosion (water, wind, ice, or gravity) carry and move these pieces. The earth's surface is constantly changing because some rock is worn away, and then after erosion deposits the rock, new rock can be formed in a different location.

2. Mechanical weathering physically breaks rock into smaller pieces, but chemical weathering breaks rock down through chemical changes.

3 and4. SEE TABLES

5. Two aspects of the type of rock can change the rate of weathering: mineral composition and perm ability.
The mineral composition in important because only some minerals are soluble (able to dissolve) in water. If a rock contains minerals that are soluble in water, then it will weather more quickly.
Permeability is important because if a rock is permeable, water can seep into the rock. Water can then weather the rock more quickly because it can weather the inside of the rock too.

6. Climate can affect the rate of weathering. Weathering occurs more quickly in hotter climate than cold one (because chemical reactions happen faster at warmer temperatures. Weathering also occurs more quickly in wet climate (water is necessary for chemical weathering and for freezing and thawing to occur). The type of climate in which rock weathers the fastest is a hot and wet climate.

Recent Chilean Earthquake

On February 27, 2010, and 8.8 magnitude earthquake shook Chile. The epicenter was off the coast of Maule, Chile, 115 km from the more populated city of Concepcion. This epicenter is not far from the epicenter of the 9.5 magnitude 1960 quake.

More info at USGS.gov


Video of Earthquake