Warm-Up
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Transcript of Warm-Up
Warm-UpWarm-Up
How would you describe the difference between a new tombstone and one that is
100 years old?
The Effects ofThe Effects of Weathering Weathering
• Weathering is the process that breaks down rocks and other substances at Earth’s surface
Sierra Nevada Mtns. ~20 myo Appalachian Mtns. ~250 myo
Two Types of WeatheringTwo Types of Weathering
• Mechanical Weathering – (also called physical weathering)
– rock is physically broken into smaller pieces without changing what the rock is composed of
Two Types of WeatheringTwo Types of Weathering
• Mechanical Weathering – (also called physical weathering)– rock is physically broken into smaller pieces without changing
what the rock is made of
Examples:• Abrasion—grinding
away of rock by other
rock particles carried
by water, ice, wind,
or gravity
Two Types of WeatheringTwo Types of Weathering
• Mechanical Weathering – (also called physical weathering)– rock is physically broken into smaller
pieces without changing what the rock
is made of
Examples:• Ice wedging—water freezes
and expands, acting like a
wedge that pushes open
cracks in rocks
Two Types of WeatheringTwo Types of Weathering
• Mechanical Weathering – (also called physical weathering)– rock is physically broken into smaller pieces without changing
what the rock is made of
Examples:• Exfoliation—layers
of rock crack and
flake off when
pressure is removed
from the rock
Two Types of WeatheringTwo Types of Weathering
• Mechanical Weathering – (also called physical weathering)– rock is physically broken into smaller pieces without changing
what the rock is made of
Examples:• Plant growth—roots
grow into cracks in
rocks and pry cracks
farther apart
Two Types of WeatheringTwo Types of Weathering
• Mechanical Weathering – (also called physical weathering)– rock is physically broken into smaller pieces without changing
what the rock is made of
Examples:• Animal action—animal
burrowing breaks apart
rocks in the soil
Two Types of WeatheringTwo Types of Weathering
• Chemical Weathering – rocks are made of minerals
– rock is broken down by chemically changing the minerals that makes up the rock into new minerals
Two Types of WeatheringTwo Types of Weathering
• Chemical Weathering – rocks are made of minerals– rock is broken down by chemically changing the minerals that
makes up the rock into new minerals
Examples:• Water—water
dissolves minerals
in some rocks
Two Types of WeatheringTwo Types of Weathering
• Chemical Weathering – rocks are made of minerals– rock is broken down by chemically changing the minerals that
makes up the rock into new minerals
Examples:• Oxidation—oxygen
reacts with minerals
(iron) in some rocks
(“rusting”)
Two Types of WeatheringTwo Types of Weathering
• Chemical Weathering – rocks are made of minerals– rock is broken down by chemically
changing the minerals that makes up the rock into new minerals
Examples:• Carbonic acid—carbon
dioxide and water form carbonic acid which reacts with minerals (marble & limestone) in some rocks
Two Types of WeatheringTwo Types of Weathering
• Chemical Weathering – rocks are made of minerals– rock is broken down by chemically changing the minerals that
makes up the rock into new minerals
Examples:• Living organisms—
plant roots & lichens (plant-like organisms) produce weak acids that can dissolve some minerals in rocks
Two Types of WeatheringTwo Types of Weathering
• Chemical Weathering – rocks are made of minerals– rock is broken down by chemically changing the minerals that
makes up the rock into new minerals
Examples:• Acid Rain—burning
fossil fuels releases chemicals into the air that react with water to form acids which can dissolve rocks
Rate of WeatheringRate of Weathering
• How fast rocks are broken down depends on:
-Type of rock
-Climate
Rate of WeatheringRate of Weathering
• How fast rocks are broken down depends on:
-Type of rock• some rocks are made
of minerals that
dissolve easier
Example:
limestone contains calcium
that dissolves easily
Rate of WeatheringRate of Weathering
• How fast rocks are broken down depends on:
-Type of rock• some types of rock
are permeable (they contain tiny holes that absorb water), so they weather faster
Example: marble is more permeable than slate
Marble 1897Slate 1856
Rate of WeatheringRate of Weathering
• How fast rocks are broken down depends on:
-Climate• Mechanical & chemical
weathering occur faster in places that are wet (have more rain)
Example: pyramids in Egypt have weathered slowly because of dryness of desert
Egypt ~4500 yo
Mexico ~1800 yo