Download Rocks Rock!

Rocks Rock!
Why?
•All Earth’s processes such as volcanic
eruptions, mountain building, erosions and
even earthquakes involve rocks and
minerals.
•Rocks are clues to the geologic past—For
example, a rock with shell fragments and
impressions probably formed in a shallow
ocean environment. Rocks tell Earth’s
stories!
Rocks
• A rock is a naturally occurring solid
mass of mineral or mineral-like material.
• Most rocks are made of two or more
minerals.
• Three major types of rocks—igneous,
sedimentary, and metamorphic
Rock Cycle
The rock cycle is the continuous
processes that cause rocks to change.
Use the diagram to answer…
• What processes form sedimentary rocks?
compaction and cementation
• What type of rock is formed by cooling
magma or lava?
igneous
Rock Cycle
• Heat from the Earth’s interior drives
the formation of both igneous and
metamorphic rocks.
• Weathering and erosion are processes
that produces sedimentary rocks.
Energy from the sun drives weathering
and the movement of sediments.
Igneous Rocks
• form from molten rock (either magma or
lava)
• magma—molten rock below the Earth’s
surface
• lava—molten rock that has reached the
Earth’s surface
• Igneous is derived from the Latin word ignis
which means “fire.”
Classification of Igneous Rocks
Classification
of Igneous Rocks
Intrusive Igneous Rocks
• Form when magma cools and hardens
beneath the Earth’s surface
• Magma is less dense than the surrounding
rock and so it rises and cools
• Large magma bodies can take tens of
thousands of years to cool.
• Intrusive rocks are found at the surface
due to weathering, faulting and mountain
building.
• As the magma cools, elements combine
to form minerals that grow in size
forming interlocking grains.
• Granite is a common intrusive igneous
rock.
Extrusive Igneous Rocks
• Form when lava cools and hardens on the
Earth’s surface
• Cools more quickly which produces a
much finer grain size
• Rhyolite is a typical extrusive igneous
rock.
Igneous Rock Classification
• Based on texture and composition
• Texture—size, shape, and arrangement
of crystals in the rock
• Composition—proportions of light and
dark minerals
Texture
Coarse
Grained
Fine
Grained
Glassy
Description
•Large crystals
•Slow cooling
Rock
Granite
•Small mineral grains
•Rapid cooling
No visible crystals
•Large crystals in
fine grained rock
Porphyritic
•Different rates of
cooling
Rhyolite
Obsidian
Pumice
Andesite
Drawing
fine grained
coarse grained
porphyritic
glassy
Three Basic Compositional Groups
Granitic Composition
• Large percentage of Si and Al
• Light colored rocks
• Contain large percentage of K-feldspars
and quartz
• Typical of continental crust
Three Basic Compositional Groups
Basaltic Composition
• Large percentage of Fe and Mg
• Dark colored rocks
• Contain large percentage of plagioclase
feldspars, biotite, and hornblende
• Typical of oceanic crust
Three Basic Compositional Groups
Andesitic Composition
• Intermediate percentage of light and
dark minerals
• Contain at least 25% dark colored
minerals—biotite, hornblende, and
pyroxenes