gel 1 - week 6

physical weathering

breaks rocks mechanically without changing their chemistry

jointing

natural cracks from pressure release

root wedging

roots grow into cracks and split rocks apart

frost wedging

water freezes in cracks, expands, and breaks the rock

chemical weathering

breaking down rocks by changing their minerals chemically

inorganic dissolution

acidic rain water completely dissolves minerals

biological chemical weathering

living things use organic acids to eat rocks

differential weathering

minerals wear away at different speeds

erosion

picking up and removing sediment

transportation

moving sediment away

deposition

dropping sediment off

lithification

turning loose sediment into solid rock

clastic rock

rock made from glued-together pieces of older rocks

clast size

how big the pieces are

clast composition

what the pieces are made out of

angularity

sharp vs. round edges

sorting

how uniform the grain sizes are

sediment maturity

how evolved the sediment is

cement character

the mineral glue holding grains together

controls on rock nature

source rock and travel distance determine the final rock

biochemical rock

made from dead animal shells and skeletons

biochemical limestone

calcium carbonate marine shells packed together

chert

glassy rock made from tiny plankton skeletons

organic rock

made from organic plant and animal tissues, not shells

coal

squeezed and heated swamp plants

oil shale

rock packed with organic kerogen that makes oil

chemical rock

minerals left behind when water evaporates or changes

travertine

limestone formed instantly at hot springs

cave carbonates

stalactites and stalagmites grown from dripping cave water

evaporites

minerals left behind when water evaporates

layers and bedding

horizontal stripes of sediment showing different time periods

ripple marks

small sand waves from water currents or wind

cross bedding

slanted internal lines from moving sand dunes

turbidites

undersea landslide deposits that are coarse at the bottom, fine at top

surface markings

clues left on top of the mud before it hardened

footprints

animal tracks frozen in stone

scours

grooves dug into mud by a heavy currentd

dehydration cracks

mud cracks formed when wet ground dries out

depositional environment

the specific setting where sediment lands

terrestrial

• land environments

• makes conglomerate, arkose, sandstone, shale

marine

• ocean environments

• makes limestone, deep-sea muds

coastal

• beaches and deltas

• makes sandstone and shale

sedimentary basin

a sinking sinkhole in the crust where sediment piles up

transgression-regression cycles

sea levels rising and falling over time