rocks are classified by how they formed and what they’re made of there are 3 general classes of...
Post on 03-Jan-2016
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• Rocks are classified by how they formed and what they’re made of
• There are 3 general classes of rocks:– Igneous–Sedimentary–Metamorphic
• Extrusive: are formed once magma reaches the surface (lava) and cools – Ex: basalt, pumice
• Intrusive: are formed from magma that cools and solidifies within the crust, which may later be uncovered by the process of erosion – Ex: granite gabbro
• Formed by wind, water, snow or organisms breaking down other rocks into sediments
• Most sediments are deposited on the bottom of lakes, rivers and seas, and then compressed to form rock.
• Cover about 75% of Earth’s surface• Many sedimentary rocks have been moved
by water, wind, waves, currents, ice or gravity.
sandstone
limestone
chalk
shale
Halite (rock salt)
coal
Common examples
Metamorphic rocks form when existing rocks are heated or squeezed; they recrystallize and might change chemically.
• All kinds of rocks can be changed• Can change the crystal structure, texture,
or can form new minerals
gneiss
marble
limestone
granite
In the rock cycle, rocks change from one type to another over millions of years.
A rock in any part of the cycle could become any other kind of rock.
Igneous Rocks
Sedimentary
Rocks
Metamorphic
Rocks
Sediments
Magma
Heat and Pressure
Melting
Cooling and Hardening
Weathering and Erosion
cementation
A mineral is an inorganic solid material with a particular chemical makeup and orderly arrangement of atoms.
• Rocks are usually composed of two or more minerals.
• Minerals form from hardening of magma or lava
• Mineral formation clues include size and how mineral crystals fit together.
• Solid materials with a repeating pattern of atoms are called crystals.
• Cleavage- splitting into thin sheets
• Fracture- breaking into rough edges
• Color- many different colors, not mineral specific
• Shape (habit)- special arrangement of atoms, if grown unimpeded
• Luster- describes how light reflects from a mineral’s surface.
• Streak- is the color powder produced when a mineral is scratched on an unglazed white tile.
• Hardness- Moh’s scale is used to classify minerals from 1 (softest, talc) to 10 (hardest, diamond). It is also a test of which minerals scratch or are scratched by others.
• Other properties of minerals include: magnetism, double refraction,
taste, or reactions with acid.
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