Transcript Rock Cycle Slideshow

Understanding Rock and
Mineral Formation and
Change
Igneous Rocks
• Igneous means “born of fire”
Igneous rocks are created by cooling of molten
magma
What is a rock?
A rock is a solid mixture of minerals.
Ex: Quartz, feldspar, mica and
hornblende combine to form granite
Intrusive Igneous
Rocks
•Form or crystallize within the earth
•Cool slowly and therefore form large
crystals
•Considered “coarse grained”
•Examples are granite and gabbro
Granite
Gabbro
Extrusive Igneous Rocks
• Form above the surface
• Lava cools quickly when exposed to
air
• Forms small crystal
• Fine grained texture
• Frothy texture
• Glassy texture
• Examples: Basalt and Obsidian
Relationships between:
• Magma depth
• Cooling rate
• Crystal size
Textures
Frothy Texture
Fine grained texture
Basalt
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Basalt (continued)
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The most common form of igneous rock
Makes up most of the ocean floor
Smooth and velvety black
Very hard
Tiny crystals
Pumice
• Floats on water
• Trapped bubbles of carbon dioxide form
holes
Obsidian
Glassy texture
Sedimentary Rocks
• Form on surface of the earth
• Often layered (bedded)
• May contain fossils or evidence of living
organisms
Weathering
• In order to understand how sedimentary
rocks form, one must understand how
existing rocks are broken down by physical
and chemical weathering
• Weathering prepares rocks for erosion and
transforms rocks into the raw materials that
will become sedimentary rocks
• Two types: Chemical and Physical
Weathering (continued)
• Weathering refers to the group of destructive
processes that change the character of the rock at
or near the earth’s surface
• Mechanical weathering breaks rock into smaller
pieces: an example is water freezing and
expanding in cracks causing rock to break apart
• Exposure to carbon dioxide and water can cause
Chemical weathering as well
Erosion and Weathering
• Once weathering has occurred, erosion – the
picking up and physical removal of rock
particles can happen quickly
• Finally, weathered and eroded material can
be transported by rivers, streams and
glaciers
• What are some methods of erosion?
Water Erosion
Wind Erosion
Examples of
Weathering
Examples of Erosion
How sedimentary rocks form:
Compaction, cementation and crystallization
Types of Sedimentary
Rocks
• Clastic: compaction and cementation
of sediments or rock particles (shale)
• Chemical: precipitation of minerals
from solution (limestone)
• Organic: consolidation of the remains
of plants and animals (coal)
How can you spot a Sedimentary
Rock?
• Sedimentary rock will often have bands or layers
across
• It will often contain fossils which are fragments of
animals or plants preserved within the rock
• The rock will tend to scrape easily and crumble
easily
Examples of Sedimentary
Rock
• Sandstone
Limestone
• Fossiliferous
Limestone
Coquina
Shale
Metamorphic Rocks
• Formed from either existing igneous or
sedimentary rocks
• Formed under tremendous heat and pressure
• Do NOT melt
• Formed deep underground
• Associated with mountain building
• Often foliated or flaky
Classifying Metamorphic Rocks
• Foliated: seems to
have layers or thin
lines – appears almost
flakey
Foliated
• Nonfoliated: Uniform
in composition – no
lines or obvious layers
Nonfoliated
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Quartzite
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Marble
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Hornblende
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Schist