1: Rocks Flashcards
What is a rock?
an aggregate of minerals and/or a mass of glass
How are igneous rocks formed?
formed by the soldification (cooling) of molten rock material (magma)
Igneous rocks environments of formation?
- Underground (intrusive/plutonic)
- Surface (extrusive/volcanic)
The texture of an igneous rock depends on the…
Cooling rate.
Slow cooling – Granite (coarse-grained) -> Rhyolite (fine-grained) -> Obsidian (glassy) – Fast cooling
To see if the igneous rock was above ground or under ground you look at the…
Grain size.
Extrusive (volcanic) Igneous Rocks
Basalt, Andesite, Rhyolite
Basalt
- Extrusive Igneous
- All over the solar system
- Air pockets - when this was magma there were bubbles floating around in it
Andesite
- Extrusive Igneous
- Not that common
- Finer grain texture
- Composition wise it is the same stuff as Diroite
Intrusive (plutonic) Igneous Rocks
Peridotite, Gabbro, Diorite, Granite
Peridotite
- Most abundant rock under the planet
- Make salt by melting peridotite a little bin the the mantel
- Made up of olivine
Gabbro
- Made up of pyraxene and other white minerals
- Pretty common rock
Diorite
- Amphabole
- Not that common
Granite
One of the most common rock in the continental crust
Igneous intrusions
Dikes, Plutons, Batholiths
Dikes
Tabular intrusions that cut across structures in adjacent rocks
Plutons
Irregular or blob-shaped intrusions ranging from tens of meters to tens of kilometers across
Batholiths
Vast areas intruded by numerous plutons
Why are intrusive rocks now exposed at the surface?
- Crust is being eroded away on the mountain chain
- Uplift is bring up the pluton
Sedimentary rocks are what percent of rocks at Earth’s surface?
75%
How are most sedimentary rocks are composited
They are mostly stratifed (layered)
Two types of sedimentary rocks
Detrital (clastic) and Chemical
How are Detrital (clastic) sedimentary rocks formed?
formed from fragments of pre-existing rocks
How are Chemical sedimentary rocks formed?
formed from minerals precipitated from water
Mud grain size/rock(s)?
- Feels smooth on teeth
- Mudstone
- Shale - if splits along thin layers
Silt grain size/rock(s)?
- Feels gritty on teeth
- Siltstone
Sand grain size/rock(s)?
- Visible grains to 2mm
- Sandstone
Gravel/Boulders grain size/rock(s)?
- Visible grains more than 2mm
- Conglomerate - if fragments are rounded
- Breccia - if fragments are angular
List of Chemical Sed Rocks?
Rock salt, Gypsum, Limestone, Coal
Rock salt - origin/other features
- Evaporation of sea or saline lake water
- light-colored, tastes salty
Gypsum - origin/other features
- Evaporation of sea or saline lake water
- light colored, soft
Limestone - origin/other features
- Precipitation of calcium carbonate from sea or lake water
- Gray, fizzes in acid (calcite), may contain fossils
Coal - origin/other features
- Buried plant material
- black, may contain plant fossils, burns
Define metamorphic rock
Rocks which have been changed by effects of heat and pressure
metamorphic rock: effects of heat
- Recrystallization
- sometimes new minerals are grown
metamorphic rock: effects of pressure
- Deformation
- Foliation, aligned mineral grains
- Folds, usually contorted foliation
List of metamorphic rocks
Slate, Schist, Quartzite, Marble, Gneiss
Slate features and was originally what rock?
- fine-grained, splits into thin sheets
- originally shale
Schist features and was originally what rock?
- coarse-grained, sparkly
- originally shale
Quartzite features and was originally what rock?
- coarse-grained, very hard
- originally sandstone
Marble features and was originally what rock?
- white, fairly soft, fizzes in acid
- originally limestone
Gneiss features and was originally what rock?
- coarse-grained, light and dark bands
- originally a wide variety of rocks
Rock Cycle (full circle)
- Magma – cooling – Igneous Rocks
- Igneous Rocks – upflit – Weathering and Erosion
- Weathering and Erosion – Deposition – Sediments
- Sediments – burial and lithifiaction – Sedimentary Rocks
- Sedimentary Rocks – heat and pressure – metamorphic rocks
- metamorphic rocks – melting – magma
Rock Cycle (inner circle)
- Igneous rocks – heat and pressure – Metamorphic Rocks
- Metamorphic Rocks – Uplift – Weathering and Erosion
- Sedimentary Rocks – Uplift – Weathering and Erosion