Science Chapter 9
Terms in this set (63)
A principle that states that the geologic processes that operate today also operated in the past.
The process of wearing down and carrying away rocks.
The process that breaks down rock and other substances.
Erosion includes the removal of rock particles by ______.
wind, water, ice and gravity
______ contributes to weathering.
heat, cold, water, ice and gases
The type of weathering in which rock is physically broken into smaller pieces is called ____
_____ is the process that breaks down rock through chemical changes.
Mechanical weathering usually works _____, but eventually wears away whole mountains.
The natural agents of mechanical weathering include:
freezing and thawing, release of pressure, plant growth, actions of animals, and abrasion
______ refers to the wearing away of rock by rock particles carried by water, ice, wing, or gravity.
Wedges of ice in rocks widen and deepen crack by a process called ____.
The agents of chemical weathering include:
water, oxygen, carbon dioxide, living organisms, and acid rain
___ & ____ weathering often work together.
chemical and mechanical
creates holes or soft spots in rock, so the rock breaks apart more easily.
Water weathers some rock by
dissolving it or carrying other substances that dissolve or break down rock..
Iron combines with oxygen in the presence of water in a process called ____.
The product of iron oxidation is
rust, which makes the rock soft and crumbly and gives it a red or brown color.
As plant's roots grow,
they produce weak acids that slowly dissolve rock around the roots.
Acid rain causes
very rapid chemical weathering of rock.
The most important factors that determine the rate at which weathering occurs are
the type of rock and the climate.
The minerals that make up the rock
determine how fast it weathers.
_____ means that a material is full of tiny, connected air spaces that allow water to seep through it.
As water seeps through the spaces in the rock,
it carries chemicals that dissolve the rock, then the water removes material broken down by weathering.
Both chemical and mechanical weathering occur faster in
Chemical reactions occur faster at
___ is the loose, weathered material on Earth's surface in which plants can grow.
Soil is a mixture of
rock particles, minerals, decayed organic material, water and air
One of the main ingredients of soil comes from ____, which is the solid layer of rock beneath the soil.
Once bedrock is exposed to air, water, and living things,
it gradually weathers into smaller and smaller particles that are the most common components of soil.
The particles of rock in soil are classified by size as:
gravel, sand, silt & clay
The dark colored substance that forms as plant and animal remains decay is called ___.
The ___ of the soil is a measure of how well the soil supports plant growth.
Soil that is rich in humus generally has
Soil texture depends on the size o the
Soil that is made up of about equal parts of clay, sand, and silt is called
Loam is the best soil for
growing most plants
The ___ scale measures acidity.
A substance with a pH of less than 4 is
A substance with a pH of 7 is
neither acidic nor basic
A substance with a pH greater than 10 is
Most garden plants grow best in soil with a pH between
6 and 7.5
Soil forms as rock is broken down by
weathering and mixes with other materials on the surface.
Soil develops layer called
A ______ is a layer of soil that differs in color, texture, and composition from the layers above and below.
The __ horizon forms as bedrock begins to weather and rock breaks up into smaller particles.
The __ horizon is made up of topsoil.
A crumbly, dark brown soil that is a mixture of humus, clay, and other minerals is called ___.
The __ horizon, often called subsoil, usually consists of clay and other particles of rock, but little humus.
Most plants grow best in
The thickest, most fertile soil forms in climate regions with
moderate temps and rainfall
___ are the organisms that break the remains of dead organisms into smaller pieces and digest them with chemicals.
Soil decomposers include:
fungi (such as mushrooms), bacteria, worms, animal waste and other organisms
A ___ is anything in the environment that humans use.
__ is one of Earth's most valuable natural resource.
It can take hundreds of years for just a few
centimeters of soil to form
The value of soil is reduced when soil loses its
fertility, and when topsoil is lost due to erosion.
Whenever soil is exposed,
water and wind can quickly erode it.
___ is the management of soil to limit its destruction.
Animals that burrow in the ground-including moles, gophers, prairie dogs, and some insects- loosen, and break apart rocks in the soil.
Freezing and Thawing
When water freezes in a crack or rock, it expands making the crack bigger. The process of frost-wedging widens cracks in sidewalks and causes pot holes in streets.
Plant roots enter cracks in rocks. As the roots grow, they force the cracks apart.
Release of Pressure
As erosion removes material from the surface of a mass of rock, pressure on the rock is reduced. This release of pressure cause the rock to crack and flake.
Sand and other rock particles that are carried by wind, water or ice can wear away exposed rock surfaces like sandpaper on wood.
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