Earth Systems Exam

exam 1

metamorphism:

heat, pressure, and fluids

-convert a parent rock into a metamorphic one

-transformation of rock WITHOUT melting

-changes their mineral composition

-all occurs under the melting point

where does metamorphic activity usually occur?

below the surface

how are metamorphic rocks distributed across the world?

1) shields: oldest part of the continental crust 

2)cores of large mountain ranges 

Agent of change—> temperature 

-the heat comes from the interior of the earth

-the heat helps speed up reactions, producing a different rock 

agent of change—> pressure

1) confining/ lithostatic

2)directed/ differential

confining/ lithostatic pressure

equal pressure in all directions due to overlying rocks

directed/ differential pressure

pressure is more in one particular direction

Agent of change—> chemically active fluids

hydrothermal fluids: water can accelerate chemical changes. aids in recrystallization of minerals by dissolution and deposition

metamorphic environments

1)hydrothermal (divergent zones)

2)contact/ thermal

3)dynamic 

4) regional

hydrothermal (divergent zones) metamorphic environment:

hot, iron rich fluids move through cracks in the rock

contact /thermal metamorphic environments

rocks surrounding a molten, igneous body are “baked”.

-form under high temp and low pressure 

dynamic metamorphic environments:

caused by faults where crust fractures due to tectonic activity

-increased pressure due to convergence, high pressure builds up but temp is low

regional metamorphic environments:

-most common

-broad range. temp and pressure both act as driving forces for metamorphic reactions

foliated texture classification:

banded appearance, associated with regional metamorphism.

-crystals are elongated or plated

-form a graded series of gran size and the development of foliation 

Non-foliated texture classification

associated with contact metamorphism.

-crystals are equidimensional 

-do not exhibit preferred orientation of minerals 

ex) marble 

grade

described by the degree to which a rock has undergone metamorphic change

“how much was this parent rock effected by the agents of change?”

what are the metamorphism grade scale transitions?

1)slate

2)phyllite

3)schist

4)gneiss

5)quartzite 

6)marble

features of metamorphic slate

-parent rock is shale and sandstone

-foliated 

-low grade 

features of metamorphic phyllite

-parent rock is shale/ sandstone

-foliated

-low-medium grade

features of metamorphic schist

-parent rock is shale and sandstone

-foliated

-low-high grade

features of metamorphic gneiss

-parent rock is shale/ sandstone

-foliated 

-high grade 

features of metamorphic quartzite

-parent rock is sandstone

-non foliated 

-medium-high grade 

features of metamorphic marble

-parent rock is limestone

-nonfoliated

-low-high grade

lakes represent what depositional environment?

continental

if a sedimentary rock contains particles at least 2mm in size, what is it grained?

fine grained

biochemical/ bioclastic

classified by the presence of once living organisms contained within the rock

chemical classification of sedimentary rock

classified by the minerals found within the rock as they were precipitated from solution

how are detrital rocks classified 

classified on size of the particles of sediment 

what sedimentary rocks are derrived from biochemical limestone?

-coquina

-chalk 

what sedimentary rocks are derived from chemical chert?

flint and jasper

is rock salt igneous, metamorphic, or sedimentary?

sedimentary

what is the most abundant chemical/ biochemical rock and also derived from calcite?

limestone

cross bedding

changing drn of flow of wind or water that changes the direction of sediment buildup

silicates

-90% of earths crust

-basic building block of silicon-oxygen tetrahedron

silicon-oxygen tetrahedron

-building block of all silicate minerals

-overall charge of +4

common dark silicates (ferromagnesian)

-olivine 

-pyroxene group (augite)

-hornblende

-micah

common non-ferromagnesian (light) silicates

-muscovite (light micah) 

-feldspar 

-quartz

light silicates

have lower specific gravity

-light in color 

dark silicates

-higher specific gravity

-rich in iron and magnesium 

what common mineral has a conchoidal fracture?

quartz

feldspar

-2 planes of cleavage

-white and pink type 

-hardness of 6 

olivine group

forms small round crystals with no cleavage

granular look in large samples 

pyroxene group (augite)

cleaves at 90 deg

dominant mineral in basalt

amphibole group (hornblende)

cleaves at 60 or 120 deg

found in continental rock

volatiles

gasses dissolved in the melt , including H20, CO2, and SO2

Basaltic (mafic) magma

most common

-dark silicate 

-hottest 

andesitic (intermediate) magma

-intermediate temp

-has a mix of dark and light silicates

rhyolitic (felsic) magma

-coolest

-light silicates 

what are igneous rocks classified by?

-texture

-location of formation 

-cooling process 

-composition 

phaneritic (intrusive) igneous rock textures

slow cooling

-coarse grained

-large crystals 

aphanitic / extrusive igneous rock texture

rapid rate of cooling of lava

-small crystals 

-fine grained texture 

glassy aphanitic igneous texture

microscopic crystals

-cools instantly with contact with water

vesicular aphanitic igneous rock texture

contains vesicles (holes from gas bubbles)

porphyritic igneous rock texture

formed at different temps and rates throughout the rock

-large crystals are called phenocrysts (rest is the groundmass)

pyroclastic igneous rock texture 

rocks form from explosive volcanic activity