Igneous Rock Types & Processes PDF

What are igneous rocks? Rocks that formed from a melt that cooled (other melted rocks) Magma= intrusive/plutonic rocks Lava= extrusive/volcanic rocks Difference between Magma and Lava Magma is underground, lava is above ground Difference between felsic, intermediate, ultramafic, and mafic magma Fe...

What are igneous rocks? Rocks that formed from a melt that cooled (other melted rocks) Magma= intrusive/plutonic rocks Lava= extrusive/volcanic rocks Difference between Magma and Lava Magma is underground, lava is above ground Difference between felsic, intermediate, ultramafic, and mafic magma Felsic: Feldspar & Quartz, high silica content >65% Intermediate: 53-65% silica Ultramafic= 100+ km^2, biggest pluton Laccolith: Mushroom or lens shaped pluton Dike: Tabular, discordant pluton Sill: Tabular, concordant pluton See Lec 6 for pics What is a supervolcano? Give an example. The term "supervolcano" implies a volcanic center that has had an eruption of magnitude 8 on the Volcano Explosivity Index (VEI), meaning that at one point in time it erupted more than 1,000 cubic kilometers (240 cubic miles) of material. Example: Yellowstone Caldera What are hot-spot volcanos? Where do they occur? In geology, a hotspot is an area of the Earth’s mantle from which hot plumes rise upward, forming volcanoes on the overlying crust. They form over exceptionally hot parts of the mantle. What does a hot-spot track indicate? A chain of volcanoes (hotspot track) forms as a tectonic plate moves over a plume of hot mantle material (hotspot) rising from deep within the Earth. Describe different forms of subaerial volcanoes (stratovolcanos, cinder cones, and shield volcanos) Stratovolcanos: Have steep sides formed by alternating layers of thick, nonflowing lava and ash Cinder Cones: A small, steep-sided volcanic cone formed by the accumulation of small, solidified lava fragments (called cinders or scoria) that are ejected from a single vent during an eruption, creating a cone shape with a bowl-shaped crater at the top Shield Volcanos: Gently sloping, wide volcano formed by very runny lava Difference between Pahoehoe and a’a’ Pahoehoe: Lava flow that is characterized by ropey, smooth, or billowy surface A’a’: Lava flow with a rough surface and a thick interior Difference between ash, Lapilli, and bomb Pyroclastic debris of varying sizes Ash: 64mm What are pillow lavas? A formation that occurs from lava erupting underwater and cooling quickly, causing a pillowy appearance Difference between Basaltic and rhyolitic lavas in terms of silica content Basaltic: mafic=low silica content Rhyolitic: high silica content Which transport medium carries the largest particles (ice, water, or wind)? Ice Explain the difference between weathering, erosion, and transportation Weathering: Breaking down of rocks where they are in place Physical- frost wedging, abrasion, exfoliation Chemical- three types, Dissolution, Oxidation, Hydrolysis Biological- Tree roots, burrowing animals Erosion: Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement Transportation: Transport refers to the processes by which the sediment is moved along – for example, pebbles rolled along a river-bed or sea shore, sand grains whipped up by the wind, salts carried in solution. What is the difference between lithification and diagenesis? Lithification: the process by which sediments are compacted of cemented together to form sedimentary rock Diagenesis: The chemical, biological, or physical process by which sedimentary rocks after sediments are deposited How do you classify chemical and biochemical sedimentary rocks? (Grain size or mineral composition)? Unlike clastic rocks, chem and biochem are classified by their mineral composition rather than grain size Difference between transgressions and regression Transgression: When the sea level rises relative to land causing the sea to flood previously dry land Regression: when sea level falls relative to land What is the difference between metamorphism and diagenesis? Metamorphism: Rocks are transformed into a much denser, more compact rock with different mineral compositions and textures Diagenesis: When sediment is changed into sedimentary rock through means of dissolution or compaction Give examples of foliation (schistosity, compositional banding) An example of foliation in geology is the layered appearance seen in metamorphic rocks like slate, schist, and gneiss where mineral grains are aligned in parallel planes, creating a distinct banding or striped pattern due to the pressure applied during metamorphism Difference between Regional Dynamothermal metamorphism and Thermal or contact metamorphism? RDM: When a rock is exposed to high heat and pressure over large areas causing new rocks to form CM: Change in minerality due to heat from magma or other rocks basically cooking the rock What is protolith in metamorphism The original rock, before undergoing metamorphosis A protolith may belong to any of the primary rock types, true or false? True What is the pressure and temperature condition for the formation of a Blueschist? High pressure, low temp, 200-500 C What is an Aureole in metamorphism An aureole is the zone surrounding an intrusion, which is a mass of igneous rock that solidified between other rocks located within the Earth. Describe the characteristics of a non-foliated metamorphic rock? Give examples. Quartzite, marble, hornfels, do not have a plated texture, typically grow crystals in no particular direction