As you observe the following pictures think about this… Have the landforms undergone changes?
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Transcript of As you observe the following pictures think about this… Have the landforms undergone changes?
As you observe the following pictures think about this…
• Have the landforms undergone changes?• What do you think caused the changes?• How long do you think the changes may have
taken?• Were the changes constructive or destructive?
Notes: Rocks and WeatheringWhat breaks down rocks?
Erosion – is the process of wearing down and carrying away rocks. (breaking of rocks into smaller pieces and the removal of rock particles by wind, water, ice, or gravity)
Weathering – is the process that breaks down rock and other substances. (heat, cold, water, ice, and gases all contribute)
Both involve the breaking down of rocks into smaller pieces, but erosion also involves the removal of rocks once they are broken.
Erosion and weathering change Earth’s surface continuously, or without stopping. They are destructive forces that act to break and wear down the surface.
What causes weathering?Mechanical Weathering – rock is physically broken down into smaller pieces
Agents of Mechanical Weathering:
Name the agents of mechanical weathering:Plant Growth
Release of Pressure
Freezing and Thawing
Abrasion
Animal Actions
What causes weathering?Chemical Weathering – the process that breaks down rock through chemical changes
Agents of Chemical Weathering:WATER
Water weathers some rocks by dissolving it.
Water also carries other substances that dissolve
or break down rock, including oxygen, carbon
dioxide, and other chemicals
LIVING ORGANISMSAs a plant’s roots grow,
they produce weak acids that slowly dissolve rock
around the roots. Lichens – plantlike
organisms that grow on rocks- also produce
weak acids
ACID RAINRainwater is naturally slightly acidic. Burning coal, oil, and gas
for energy can pollute the air with sulfur, carbon, and nitrogen compounds. These compounds react with water
vapor in clouds, making acids that are stronger than normal rainwater. These acids mix with raindrops and fall as acid rain. This causes very rapid chemical weathering of rock.
OXYGENThe oxygen gas in air is an
important cause of chemical weathering. Iron combines
with oxygen in the presence of water in a process called
oxidation. The product of iron oxidation is rust. Rust makes rocks soft and crumbly and
gives it a red or brown color.
CARBON DIOXIDEAnother gas found in air.
Causes chemical weathering when it
dissolves in water. The result is carbonic acid.
Carbonic acid easily weathers some kinds of
rocks, such as marble and limestone.
LET’S REVI EW:Mechanical – means by physical processes
(like a physical change – a change in size, shape, state; the change does not alter the makeup of the substance)
Chemical – suggests processes related to chemical reactions (like a chemical change – changes resulting from chemical
reactions, in which substances change into other substances)
Chemical and mechanical weathering often work together. Chemical weathering creates holes of soft spots in rock, so the rock breaks apart more easily.As rocks break into pieces, more surface area is Exposed to chemical weathering.
How fast does weathering occur?The most important factors that determine the rate at which weathering occurs are the type of rock and climate.
Type of Rock• Minerals in the rock determine how fast it weathers. Rocks weather faster if they are made up of minerals that dissolve easily. • Some rocks will weather faster if they are permeable – full of tiny, connected air spaces that allow water to seep through it. As water seeps through the spaces it carries chemicals that dissolve the rock. Climate• Climate is the average weather conditions in an area.• Both chemical and mechanical weathering occur faster in wet climates.
Rainfall provides water for chemical changes and freezing and thawing. • Chemical reactions occur faster at higher temperatures. So chemical
weathering occurs more quickly where the climate is both hot and wet.
SOILWhat are some examples of organisms that live in soil?
Describe soil you have seen or touched. How did it feel? How did it smell? What creatures did you see in it?