rock melting factors 5.1 lecture notes mineral composition : different minerals melt at different...
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Rock Melting
Factors
5.1 Lecture Notes
Mineral Composition:
Different minerals melt at different temperatures.
Pressure:Rocks that can withstand higher pressures required higher temperatures in order to melt.
Explain:
Explain:
Water and carbon dioxide:
H2O & CO2 help lower the pressure within a rock; thus lowering the rock’s melting temperature.
Subduction Zones
Rocks subducted along plate boundaries are subjected to increased temperatures & begin to melt.
At underwater subduction areas: rocks melt faster because pressure is reduced.
situations
Mantle plumes:Areas with hot, rising magma (mantle plumes) melt rocks as they rise.
Mantle plumes (hot spots) on Earth’s surface result in volcanoes.
situations
Divergent Boundaries:
As plates pull away from one another, a decrease in pressure occurs, and thus triggers melting.
situations
Intrusive Igneous RockDescribe:
Magma that crystallizes before it reaches earths surface.
Cooling rate: Slow.
Crystal size and texture: Large; phaneritic
Porphyritic Texture
Describe: Magma that cools slowly & then rapidly will have large crystals “floating” in smaller crystals.
Extrusive Igneous Rock
Describe: Magma that crystallizes on Earth’s surface.
Cooling rate: Rapid
Crystal Size and Texture: Small; Aphanitic
Stop here, do rest of notes another day!
Three Methods of Formation of Intrusive Igneous RocksStoping:
Pieces of older rock break from the magma chamber’s wall, drop into the magma, & melt.
Magma Chamber:
Magma Injection:Magma is forced out of magma chamber & into pre-existing fractures.
Sometimes magma crystalizes within a magma chamber.
Intrusive Igneous BodiesBatholith:
Large intrusive masses that cut across older rocks & cover areas greater than 100 sq km.
Stocks:
Laccoliths:
Large, dome-shaped intrusions injected into shallow, sedimentary rock beds.
Smaller intrusive masses less than 100 sq km.
Dikes: Small, shallow intrusions that cut across pre-existing rock.
Sills: Small, shallow intrusions that get injected parallel to the rock layers.
Pyroclasts
Describe: Fragments ejected from a volcano; includes small ashes to large rocks!
Ex: Mt. St. Helens!
Pyroclastic flow
Lava Flow
Describe: Molten rock from an erupting lava vent. Lava flow speed depends on its composition & the slope’s steepness.