GEOL 1121 Unit 2 (Sedimentary and metamorphic rocks)

Sediment

unconsolidated particles of rock found on the earth’s surface that have been transported

clastic sedimentary rock

rocks that form when sediment accumulates, becoming compacted and eventually litified

Lithification

the process of sediment grains are cemented together

Clastic rock formation process

Uplift, Erosion, Transport, Deposition, Compaction, and Lithification

Uplift

the process of tectonic plates merging to create mountains

Erosion

the process of rocks and mountains being broken down through wind, snow, and rain

Transport

wind and water move the sediment grains to deposition locations (through streams and over deserts)

deposition

the final place where sediment is carried by the wind and water

Compaction

as sediment piles up, it gets heavier weighing down the sediment in at the bottom, reducing the space between the grains

Lithification

the process whereby the minerals in impure water cements sediment grains together

Classification of sediment rocks

Shale: clay sized grains

Sandstone: sand sized grains

Conglomerate: gravel sized grains

Texture

one of the two main ways that sedimentary rocks are interpreted. the smaller and rounder grains are, the further from their source they are.

Composition

another of the two main ways that sedimentary rocks are interpreted. Minerals that are higher up on BRS are less stable, and will break down faster than minerals lower on BRS. The composition of a rock can show its distance from the point of origin

Immature sedimentary rocks

have:

sediment that is near to its source

larger grains

angular grains

lots of different minerals

Mature sedimentary rocks

Have:

sediment that is far from the source

small grains

rounded grains

a smaller number of resistant minerals

Chemical/biogenic sedimentary rocks

are formed when shallow marine areas that host algae produce extreme amounts of calcium carbonate. when those organisms die, they are calcified and turn into limestone, layering on top of each other.

Depositional environments

areas where sediment can be easily deposited for the formation of sedimentary rocks.

(dunes, lakes, beaches, barrier islands, costal shelves)

Metamorphic rocks

rocks that already existed, but undergo a change due to an outside force (whether that be mechanical or chemical)

Stress

an applied force (ex. the impact site of two continents smashing together) (Cause)

Strain

the response of an applied force (the response of minerals/rocks when two continents smash together) (Effect)

Folding

A mechanical change of metamorphic rocks that cause rocks to bend and fold under high temperatures and pressure

Preferential grain alignment

when shale undergoes extreme pressure and temperatures, they will line up parallel and create smooth flat rocks

Recrystalization

some grains, as a strain response as a result of being pressed together, will fuse and create large crystals

P/T table

A table that has Pressure on the y-axis and Temperature on the x-axis, which also contains an exponential curve line separating minerals from BRS. When crossed, minerals metamorphose into other rocks.

Contact metamorphism

a type of metamorphism due to high temperatures. This occurs near igneous intrusions and creates a halo around the magma where the rocks are metamorphosed.

Regional metamorphism

a type of metamorphism where changes in temp and pressure (usually when tectonic plates collide) cause sent underground to metamorphose

Marble

a type of metamorphic rock that occurs as a result of limestone being metamorphosed

Quartzite

the result of sandstone being metamorphosed (recrystalization)

Schist

Shale (flat aligned rock) that undergoes high temp and pressure and starts growing smaller crystals

Gneiss

Schist that continues to grow crystals, separating the rock into two layers of light and dark rocks