ROCKS ROCK!
Earth’s Layers
Compare & Contrast Rocks!
Look at the rock samples and write a short paragraph ( at least 5 COMPLETE sentences) describing how the rocks are similar and how they are different.
What is a ROCK?
Solid mass of mineral or mineral-like matter that is naturally occurring
Most rocks are made up of more than one mineral
Some rocks are made up of no minerals Coal=organic material
Three Major Types of Rocks
Igneous Intrusive Extrusive
Sedimentary Metamorphic
The Rock Cycle
Interactions among Earth’s water, air, & land can cause rocks to change from one type to another
Magma or Lava?
Magma is molten material deep beneath Earth’s surface
When magma reaches the surface it becomes lava
Important Vocabulary to Understand the Rock Cycle
Weathering—process by which rocks are physically and chemically broken down by water, air, & living things to produce sediment
Sediment—weathered pieces of earth material
What drives the rock cycle?
Igneous and metamorphic rocks are formed by processes from Earth’s interior heat
Sedimentary rocks are produced by processes on and near Earth’s surface Weathering and the movement of
weathered materials are external processes powered by energy from the sun & gravity
Think!
Turn to the person sitting next to you and discuss:
What do you notice about the rock cycle?
IGNEOUS ROCKS!!!
Igneous Rocks
Intrusive igneous rocks—form when magma hardens beneath Earth’s surface
Extrusive igneous rocks—forms when lava hardens
Quick Check
How are magma and lava the same? How are they different?
Classification of Igneous Rocks Coarse Grained Texture
Slow cooling=large crystals Fine Grained Texture
Fast cooling=small, interconnected minerals grains
Which is coarse grained & which is fine grained?
Classification of Igneous Rocks Glass Texture—no time for ions in the
lava to arrange into crystals before hardening Randomly distributed ions
Porphyritic Texture—rocks with very different-size minerals experience different rates of cooling
Classification of Igneous Rocks Granitic Composition—light-colored
silicate minerals quartz & feldspar are the main minerals Most granitic rocks contain about 10% dark
silicate minerals (such as biotite mica & amphibole)
Classification of Igneous Rocks Basaltic Composition—contain many
dark silicate minerals & plagioclase feldspar Rich in magnesium & iron Typically darker & denser than granitic
rocks because of the iron Make up Earth’s ocean floor
Classification of Igneous Rocks Andesitic Composition—between granitic
& basaltic At least 25% dark silicate minerals, mainly
amphibole, pyroxene, & biotite mica Peridotite—almost entirely dark silicate
minerals (olivine & pyroxene) Ultramafic—rare at Earth’s surface but
much of the upper mantle
Classification of Major Igneous Rocks
Rock Joke Break!
Sedimentary Rocks!!!
Formation of Sedimentary Rock Clastic Sedimentary Rocks—made of
weathered bits of rocks and minerals Chemical Sedimentary Rocks—dissolved
minerals precipitate from water solutions
Clastic Sedimentary Rocks
Made of mostly clay minerals & quartz Grouped by size of the sediments
Conglomerate=rounded, gravel-size or larger particles
Breccia=angular particles Sandstone=sand-sized grains
Chemical & Biochemical Sedimentary Rocks
Dissolved substances precipitate, or separate, from water solutions
Water evaporates or boils off leaving a solid product Ex: limestone, rock salt, chert, flint, and
rock gypsum Biochemical Sedimentary Rocks=shells
& skeletal remains of organisms that settle to the ocean floor
Features of Sedimentary Rock Each layer of sedimentary rock records a
period of sediment deposits Fossils are unique to some sedimentary
rock
Classification of Sedimentary Rocks
Metamorphic Rocks!!!
Formation of Metamorphic Rocks Existing rocks are changed by heat &
pressure What does metamorphism mean?
Come up with the best definition possible with the person next to you!
Changes form
Formation (Continued)
Contact morphism=magma intrudes (forces its way into) rock
Marble often forms when magma intrudes into limestone
Formation (Continued)
Regional metamorphism Large areas of rocks are subjected to
extreme pressures & temperatures during mountain building
Intense changes occur at a large scale level
Agents of Metamorphism
Heat Provides energy needed to drive chemical reactions Cause existing minerals to recrystallize Magma & change in temperature from depth
Pressure (stress) Increases with depth Causes the spaces between mineral grains to close Results in more compact rock with a greater density
Reactions in solution Hot solutions promote recrystallization Can deposit new minerals in the rocks
Classification of Metamorphic Rocks
Foliated metamorphic rocks Layered or banded appearance
Nonfoliated metamorphic rocks No banded texture Most contain only one mineral Marble is an example—made up of calcite
Classification of Metamorphic Rock
Think!
Use what you have learned about the rock cycle to explain the following statement: One rock is the raw material for another
rock Your friend shows you a rock with
distinct layers. How can you and your friend determine if the rock is a sedimentary rock of a metamorphic rock?