Rocks, Rocks, and More Rocks
Dec 20, 2015
Types of Rocks
• Igneous rock– Forms when magma cools and hardens – Can form underground or above ground– Types of igneous rock:
• Granite• Scoria• Pumice• Obsidian
Pumice
ObsidianScoria
• Wind and water can break igneous rock into sediments.
• When the sediments are cemented into a layer over time, igneous rock becomes sedimentary rock.
• What causes the cementation?
Types of Rocks
Sedimentary Rock
SedimentsIgneous Rock
Wind and Water
Cementation
Types of Rocks
• Sedimentary Rock– Common types include chalk, limestone, and
clay– Often contains fossils – Types of Sedimentary rocks
• Clastic: made up of different rock fragments• Biogenic: contain materials from organisms such
as corals• Precipitate: rocks formed when water evaporates
such as halite (rock salt left behind after sea water evaporates)
Types of Rocks
• Weathering and erosion will revert sedimentary rocks back to sediments.
• Heat and pressure change sedimentary rock to metamorphic rock.
Metamorphic Rock
Sedimentary Rock
Sediments
Weathering and Erosion
Heat and Pressure
Types of Rocks
• Metamorphic Rock– Make up a large part of the Earth’s crust– Common examples include slate, shale, and
mudstone– Can go through foliation, a process where the
randomly distributed minerals in the rock become organized in a parallel manner
– Foliation can cause cleavage or breakage of the rock at weak cracks
Types of Rocks
Metamorphic Rock
Sediments MagmaWeathering
and Erosion
• Very high heat melts metamorphic rock into magma.
• Weathering and erosion will change metamorphic rock back to sediments.
Melting
Magma (molten rock)
• A hot liquid made of melted minerals
• Called lava when it appears on Earth’s surface, usually from volcanic vents
• The temperature of magma can range from 650 to 1200 °C
• Created by heating rock under extreme temperatures
• Cooling magma creates igneous rock
What do compaction and
cementation do to sediments?
What does melting metamorphic rock
create?
What does cooling magma create?
What do weathering and erosion do to all types of rock?
What does the melting of igneous
rock create?
Rock Cycle
Igneous Igneous RockRock
Metamorphic Metamorphic RockRock
SedimentsSediments
Sedimentary Sedimentary RockRock
MagmaMagmaWhat do
weathering and erosion do to this
type of rock?
What do heat and pressure to do
sedimentary rock?
Weathering and Erosion
Heat and Pressure
Cementation
Cooling
Melting
Which rock becomes metamorphic rock
under heat and pressure?
Minerals
• Rocks are made up of one or more types of minerals.
• True minerals have the following characteristics:– Solid– Have a crystal structure– Inorganic and naturally occuring– Defined chemical composition
Minerals
• Ways to classify minerals:– Hardness: how hard the material is– Luster: how the surface interacts with light– Metallic: metallic qualities such as
reflectivity– Color: what color the material is– Magnetism: the rock’s ability to attract other
metals– Fluorescence: appearance under UV light
Erosion
• Erosion is the movement of particles by wind, water, ice, or gravity.
• Erosion is a natural process that can be increased by human land use.
• Steep slopes, lack of vegetation, and land use can increase the rate of erosion.
• How does erosion differ from weathering?