Geo – Chapter 4

IGNEOUS; volcanoes, freezing or slitifcation. SEDIMENTARY; pressure pushing on all the materials pushing them together, precipitation of water solutions. METAMORPHIC: changes because of environmental factors; occurs in a solid state.

Igneous.

Igneous; crust. Sedimentary; land surface.

They are formed by volcanic eruptions, creating lava flows, and then it hardening. 1. Extrusive; volcanic eruptions ->cools faster, above ground is cooler. 2. intrusive; starts under the ground and gets pushes upwards -> crystal size is smaller, so it's cooler so it's more likely to break.

plutonic: changes in magma during cooling. volcanic: eruption. intrusive: cooling under earth's surface, magma gets away from the magma chamber. extrusive: cooling above earth's surface. aphanitic: fine-grained crystals. phaneritic: bigger grained crystals. porphyritic: larger crystals surrounded by finer crystals. pegmatitic: coarse grained, cools slower. glassy: igneous rocks, felsic, high concentration of silica inhibits early growth of crystals. vesicular: rocks that have bubbles with the open holes within then. i.e. Hummus. pyroclastic: fragments that are coming out of volcanoes and then consolidate.

Magma turns into Igneous Rocks. WHERE: develop upon volcanoes apon oceanic trenches; hot spots, within continental rifts, or along ocean ridges. They can melt up decompression melting (opening of crust allowing rocks to melt, lowering the temperature), heat transfer (melting of crust), or addition of volatiles.

...pressure prevents melting, decrease in pressure permits melting. as crust heats up and melts, pressure decreases so more of the mantle magma melts. Melting is caused by a)a decrease in pressure b)by addition of volatiles c) as a result of heat transfer from rising magma. at a volcano, which is a hot spot), the increase in rising magma( from its own "buoyancy it rises and heat rising etc, all causes such pressure at the earth's crust that it explodes out like soda from a bottle. continental hot spot causes an effusive and explosive eruption (a volcano).

...the 4 groups are felsic or silicic magma (66-76%); intermediate magma (52-66%); mafic magma (45-52%);and ultramafic magma (38-45%). the 4 vary in the amounts of silica as compared to the magnesium and iron oxides contained in them. you would expect to see iron in both mafic and felsic because fic means iron. ma means magnesium so expect to see magnesium in mafic.

...viscosity means resistance to flow. it affects the speed of lava.. low viscosity flows more easily. high viscosity flows more slowly. viscosity depends on temperature, content of volatiles (additives like water and gases), and silica content. hotter magma is less viscous.more volatiles are less viscous than dry. mafic is less viscous than feltic. viscosity is like, syrup flows slower than water, cos its thicker and heavier. so viscosity means, resistant to flowing.

.the cooling time of magma . 3 factors control the cooling time; the depth of intrusion, the shape and size of the magma body, the presence of circulating ground water. exposure to air, and underground effects above. fractional crystallization is when during freezing of molten rock, cooling takes place, and many minerals form. because some crystallize first, are dense and sink, the process of fractional crystallization takes place, where sequential crystal formation happens. (some cool first, some later) this process progressively extracts iron and magnesium from the magma. the remaining magma, cools later, rises up later, and has a different composition of iron magnesium and silicates. other processes that affect it are freezing, fractional crystallization, earthquakes and underground pressure, pressure from above at the earth crust, temperatures, adding of volatiles (like water) and plate techtonics.

.sills are parallel to pre existing layers. an intrusion that injects parallel to layering. dikes cut across pre existing layers. they stick up, like a dutch dike. batholiths are an immense mass of igneous rockl the intrusion of numerous plutons in an immense area. like the sierra nevada mountains in california is a batholith. Dikes form in regions where the crust is stretched horizontally, such as a rift. sills occur near the surface of the earth. Batholiths of plutons occur with the process of stoping, when magma assimilates wall rock and pieces break off. Magma rises for two reasons. 1st is buoyancy drives magma upward bec. it is less dense than surrounding rock. 2nd is magma rises bec. the weight of over lying rock creates pressure at depth that literally squeezes magma upwards, like if you step in mud barefoot, the mud squishes up between your toes.

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