geog midterm rocks

what environments can rocks be formed in

igneous rocks - from a melt

sedimentary rocks - preexisting rocks that are weathered and deposited as particles

metamorphic rocks - preexisting rocks that have been exposed to high heat or solutions that alter them

rock cycle

eternal process of recycling rocks through erosion, deposition, subsidence, melting, cooling, uplift, or other processes

igneous rock types

felsic, intermediate, mafic, ultramafic rocks

igneous felsic rocks

fine deposited internally - rhyolite

coarse deposited externally - granite

igneous intermediate rocks

fine deposited internally - andesite

coarse, intrusive, deposited externally - diorite

igneous mafic rocks

fine deposited internally - basalt

coarse deposited externally - gabbro/norite

igneous ultramafic rocks

fine deposited internally - komatiite

coarse deposited externally - peridotite

rhyolite

lava cooled and set over 410 mil years ago, bands of different composition were stretched out into layers

pumice

extrusive rock composed of light minerals (silica and quartz)

granite

intrusive rock with visible crystals, mostly Si

scoria

extrusive rock, formed bubbles as the rock solidified, vesicular basalt with iron and magnesium

columnar basalt

extrusive mafic rock

basalt boulder

when molten, the lava gave off bubbles of gas, leaving vesicles oncce the rock had solidified, these were later filled by crystals precipitated from mineral rock water percolating through the rock

how does magma distribute as lava and pyroclastics

xenoliths

fragments of older rocks that get incorporated into younger igneous rocks (like granite or basalt) as magma moves through the Earth's crust

dyke

cuts through older lighter coloured rock

mafic sills

sheet-like intrusions of igneous rock rich in iron and magnesium (dolerite) that inject between older layers of sedimentary rock

hawaii’s hot spot and lowering

fixed as the pacific plate passes over it volcanic islands are formed

erosion causes the island to get lower and eventually becomes part of the emporer seamount

evidence for pacific plate moving

chain of islands in the seamount have changed direction indicating the pacific plate changed directions over time

what are volcanos controlled by

by the composition of the magma. this composition can change if it incorporates a significant amount of country rock

weathering

rocks break down over time through processes either physical or chemical

erosion

once rocks are broken down the product of weathering can be transported away by a number of processes

physical weathering

ice wedging, thermal (heating and cooling), salt weathering, wetting and drying

niche

cliff dwellings between sandstone and shale

solution weathering

where minerals in rock dissolve directly into water, separating into ions

salt mine

kms of salt under the mediterranean from where is dried in the tertiary

salt under pressure

salt behaves like a viscous liquid. bands likely show climate variations

sedimentary environments

fluvial, lacustrine, deltaic, shoreline, and marine

river delta

may build a delta by dropping its sediment load

turbidity currents

transport sediment down undersea canyons where they form deposits known as turbidites

turbidites

multiple form a submarine fan at the mouth of a deep undersea channel

how are beaches formed

waves and tidal currents then redistribute some of the sediment

strong currents affect on river bend

erodes the river bank and only coarser material settles to the bottom, the stronger the current also leads to the development of large dunes on the channel floor

point bar

arc shaped platform that is built out from a weaker current depositing finer sand and mud

types of rivers

bedload, mixed load, suspended load channels

bedload channels

straight, meandering, braided

mixed load channels

straight, meandering, island braided

suspended load channels

straight, meandering, anastomosing

when do different minerals form

under different conditions of pressure and temp

metamorphism succession

chlorite, muscovite, sillimanite, kyanite (2 low, 2 high)

cleavage

sedimentary layers are still discernible, this slate is considered a low grade metamorphic rock

migmatite

formed deep in the crust by the partial melting of grey gneiss and later injection of pink granitic melt

colourful marble

consisting of largely orange calcite and green pyroxene from a quarry