Soil Formation

Which of the following describes how microorganisms influence the chemical characteristics of soil?

• They loosen and mix the soil by digging burrows underground.

• They add inorganic material to the soil by weathering rocks on Earth’s surface.

• They add moisture to the soil by creating pores through which water can move.

• They add organic material to the soil by breaking down the remains of plants and animals.

Tags

NGSS.MS-LS2-3

Granite has only recently been exposed at a location on Earth’s surface. How will this most likely affect the soil that will eventually form at this location?

• The soil will have a thick layer of humus in the A horizon.

• The soil will contain many of the same minerals as the granite has.

• The soil will consist of thin horizons compared to other types of soils.

• The soil will be made of mostly rock material instead of organic matter.

In which of the following soil layers is humus mostly found?

• A horizon

• B horizon

• C horizon

• D horizon

Granite has only recently been exposed at a location on Earth’s surface. What will need to happen first in order for soil to eventually form in this location?

• A thick layer of humus must form on top of the granite.

• The granite must be broken into smaller pieces by weathering processes.

• Erosion by wind and water must move pieces of granite to other locations.

• Microorganisms must begin to break down the remains of plants and animals.

Tags

NGSS.MS-ESS2-2

What is humus?

• spaces between soil particles through which water and air can move

• weathered sediment broken down by atmospheric forces on Earth’s surface

• dark, organic material formed in soil from the decayed remains of plants and animals

• a loose mixture of rock fragments, organic material, water, and air that can support the growth of vegetation

Tags

NGSS.MS-LS1-5

NGSS.MS-LS2-1

Which soil horizon typically contains the least organic matter?

• A horizon

• B horizon

• C horizon

• O horizon

Leaves release acids into the soil as they decay. How could decaying leaves affect rock in the soil beneath them?

• They could expose the rock to wind and water.

• They could decrease the amount of weathering that occurs within the soil.

• They could increase the amount of chemical weathering of rock and soil formation.

• They could decrease the amount of chemical weathering and slow down the rate of soil formation.

Tags

NGSS.MS-ESS2-1

NGSS.MS-ESS2-2

NGSS.MS-LS2-3

You have just analyzed a 100 g soil sample. You have organized your findings in the data table. Which two materials make up at least 50 percent of the composition of your soil sample?

• air and silt

• silt and sand

• air and water

• clay and organic matter

Gopher tortoises live on dry land. They live in large holes that they dig in the soil. Which statement gives the best explanation of how this behavior aids in soil formation?

• It hardens the soil, allowing less water to reach the rocks underground.

• It erodes the soil by moving it from underneath the ground to above ground.

• It loosens and mixes the soil, increasing air in the soil and the ability to drain water.

• It causes weathering of the rocks, as the tortoise breaks the rocks into smaller pieces.

Tags

NGSS.MS-LS2-3

Susan rubs two rocks together. One of the rocks wears away to form small particles. What would most likely happen if this rock continues to break into small pieces after Susan puts the rocks back on the ground?

• The pieces may become part of the soil.

• The pieces may become part of the bedrock.

• The pieces may become part of the ice wedging process.

• The pieces may become part of the organic matter in the soil.

Tags

NGSS.MS-ESS2-1

NGSS.MS-LS2-3