Upload
william-young
View
220
Download
0
Embed Size (px)
Citation preview
3 Types of RocksDecember 9, 2015
7th grade Chapter 9.3-9.5
Scientist of the Day
Rita Levi-Montalcini• Wanted to be a writer; twin
sister a painter• Friend died of cancer –
decided to be a doctor instead• Lost job in WWII Italy because
she was Jewish• Started working in her
bedroom, then as a refugee• Discovered how nerves grow• Won 1986 Nobel Prize in
medicine
Rocks vs Minerals• Rocks are usually mixtures of minerals and other
componentso Can be 1 mineral or several
• 4 main traits to classify rocks:
1. Mineral composition2. Color3. Texture4. Origin
Rock Origins• 3 major groups for rocks• Determine rock group based on other properties
Igneous rock: formed from cooling magma or lava
Sedimentary rock: forms when particles of other rocks, plants, or animal remains are pressed and cemented together
Metamorphic rock: when a rock is changed by heat, pressure, or chemical change, usually deep underground
Igneous Rocks• Formed from magma or lava, which is high in
silica• When it forms below the crust, it’s called
intrusive• Above the crust, extrusive
Trends (Not Always True):• High in silica = dark rocks• Low in silica = lighter-colored rocks• When it cools quickly, it’s hard to form big
crystals, so very fine grains in the texture.• Hard, dense, and durable = good for arrowheads,
countertops, fortresses
Sedimentary RocksSediment: small, solid particles of rocks or living things
• Sedimentary rocks form when sediment is deposited by water or wind and eventually stuck together
• Usually soft• Sandstone and limestone are important building
materials – sometimes used to make concrete too
Forming Sedimentary Rocks
Weathering & Erosion Deposition Compactio
nCementati
on
3 Types of Sedimentary Rocks
Clastic rock: rock fragments are squeezed together. Classified according to how big the particles are. E.g. conglomerate, shale, sandstone
Organic rock: formed when remains of plants or animals are pressed together. E.g. coal from swamp plants, limestone from shells & skeletons that are high in calcium
Chemical rock: usually formed from solutions. E.g. Rock salt, limestone when it’s from evaporation
Metamorphic Rocks• Start off as sedimentary or igneous rocks, then
are changed by heat, pressure, chemical changes, or a combo of these processes. E.g. marble, slate
• Appearance, texture, and crystal structure of the minerals changes
• Classified by pattern of the grains• Used as building materials, old blackboard, etc.• Most metamorphic rocks are foliated
Foliated: thin, flat layers in a rock