Download Weathering

Weathering
The Earth’s Changing Surface
Weathering
• the process that breaks down rock and
other substances at Earth’s surface
Erosion
• The removal of rock particles by wind,
water, ice, or gravity.
How fast can it fizz?
• Place a “rock” into the first beaker
• Crush a second “rock” and place it into the
second beaker
• Add the water to the beaker with the full
rock. Time how long it takes for the “rock”
to dissolve.
• Add the water to the beaker with the
crushed “rock.” Time how long it takes to
dissolve.
How fast can it fizz?
• Which dissolved faster, the whole “rock” or
the crushed “rock?”
• What variable affected how long it took
each of them to dissolve?
Two Types of Weathering
Mechanical
Chemical
Mechanical Weathering
• Rock is physically broken into smaller
pieces.
– These rocks have the same composition as
the rocks they came from.
Causes of Mechanical Weathering
• Ice wedging – freezing and thawing
– Causes potholes on streets
Causes of Mechanical Weathering
• Release of pressure - erosion removes
material from surface, pressure is
reduced. Pressure release causes rock to
crack.
Causes of Mechanical Weathering
• Plant growth – roots of trees and other
plants enter cracks in rocks.
Cause of Mechanical Weathering
• Actions of animals – animals that burrow
in the ground loosen and break apart
rocks in the soil.
Cause of Mechanical Weathering
• Abrasion – the grinding away of rock by
rock particles carried by water, ice, wind,
or gravity.
Chemical Weathering
• The process that breaks down rock
through chemical changes.
– Produces new minerals.
Cause of Chemical Weathering
• Water – dissolves rock
– Water is the most important cause of chemical
weathering
Cause of Chemical Weathering
• Oxygen – rust!!
– Iron combines with oxygen in the presence of
water in a process called oxidation
Cause of Chemical Weathering
• Carbon Dioxide – dissolves in rain water
– Easily weathers rocks such as marble and
limestone
Cause of Chemical Weathering
• Living Organisms – plants produce weak
acids
Cause of Chemical Weathering
• Acid Rain – how is it formed?
– Coal, oil, and gas is burned for energy
– These fuels pollute the air with sulfur, carbon,
and nitrogen
– These compounds react with rainwater,
forming acid rain.
Walk!!
• Re-visit the stops on our previous walk
Rate of Weathering
• Type of Rock
– The minerals that make up rock determine
how fast it weathers.
• Marble vs. granite
• Climate
– Faster in wet climates
– Chemical reactions occur faster at higher
temperatures