Classifying Rocks
When studying a rock sample, geologists observe the rock's what?
color, texture, and mineral composition
How are igneous rocks classified?
According to their origin, texture, and mineral composition
Describe the process that forms sediments into solid rock. (hint: there are 4 steps)
erosion, deposition, compaction, cementation
Write a definition for a coral reef.
Skeletons produced by coral animals that grow together and form a structure called a coral reef.
Describe how metamorphic rocks form.
Heat and pressure deep beneath Earth's surface can change rock into metamorphic rock.
How do geologists describe a rock's texture?
Geologists will describe the size, shape, and pattern on the rock's grains.
What is the difference between extrusive rock and intrusive rock?
Extrusive rock - igneous rock formed from lava that erupted onto Earth's surface
Intrusive rock - igneous rock formed when magma hardened beneath Earth's surface.
What are the three major groups of sedimentary rocks?
clastic rocks, organic rocks, and chemical rocks
List and describe the three types of coral reefs.
Fringing reefs - lie close to the shore
Barrier reefs - lie farther out
Atolls - ring shaped coral island found far from land
How do geologists classify metamorphic rocks?
by the arrangement of the grains that make up rocks.
What are the three major groups of rocks and describe how they are formed.
Igneous - formed by the cooling of molten rock
Sedimentary - particles are pressed and cemented together
Metamorphic - when existing rock is changed by heat, pressure, chemical reactions
A rock with large crystals scattered on a background of much smaller crystals has a what texture?
Porphyritic Texture
What is an example of a Clastic Rock, Organic Rock, and Chemical Rock?
clastic - shale
organic - coal
chemical - gypsum
How can limestone that began as coral be found on land and continents?
The movement of Earth's plates slowly uplifted the ocean floor where these reefs grew until the floor was exposed and became dry land.
What is the difference between foliated and non foliated rocks?
Foliated - grains arranged in parallel layers or bands
Non foliated - grains arranged randomly
How does the silica content of magma and lava affect the formation of rocks?
Lava that is low in silica usually forms dark colored rocks such as basalt
Magma that is high in silica usually forms light colored rocks such as granite.
What are sandstone and limestone used for?
building materials and decoration.
What are some uses of metamorphic rock?
marble and slate - marble is used in many buildings and statues. slate is used in many floors, roofing, and walkways.