Rocks

Question 1

What are the three types of rocks?

Answer 1

Igneous, Sedimentary, Metamorphic

Question 2

What is igneous rock classification based on?

Answer 2

Composition and texture

Question 3

What are the three basic compositional categories?

Answer 3

Felsic (most Si rich), Intermediate, Mafic (most Ma + Fe rich)

Question 4

How do you determine compositional category of igneous rock?

Answer 4

As proporition of silica increases, density decreases; As proportion of silica increases, color becomes lighter

Question 5

What are the three textural categories of igneous rocks?

Answer 5

Crystalline, Glassy, Fragmental

Question 6

Finely crystalline

Answer 6

Rapid cooling, crystals do not have time to grow, extrusive

Question 7

Coarsely crystalline

Answer 7

Slow cooling, crystals have a long time to grow, intrusive

Question 8

Porphyritic texture

Answer 8

a mixture of coarse and fine crystals; indicates two stage cooling history

Question 9

Glassy textures

Answer 9

Solid mass of glass, or crystals surrounded by glass; results from rapid cooling; color gradient from Si to Ma&Fe does not apply

Question 10

Fragmental textures

Answer 10

Igneous fragments (pyroclasts) are spewed out of
explosively erupting volcanoes, the pieces fall and are
cemented or fused together; Ex: Tuff (lithified) or Volcanic breccia (larger fragments)

Question 11

What are the two classes of sedimentary rock?

Answer 11

Clastic and Nonclastic

Question 12

Clastic sedimentary rock consists of…

Answer 12

loose rock fragments (clasts - mineral grains & rock fragments) cemented together (w/ cementing material)

Question 13

Inclastic sedimentary rock

Answer 13

sediments derived from living organisms or minerals precipitated from a water solution

Question 14

How are clastic sedimetary rocks created?

Answer 14

Weathering (rock disintegration), erosion (removal of sediment grains from parent rock), transportation (sediment dispersal by gravity, wind, water, and ice depending on viscosity and velocity), deposition (sediment settling out of the transporting fluid), lithification (burial, compaction and cementation — transformation of loose sediment into solid rock)

Question 15

How do you classify clastic sedimentary rocks?

Answer 15

Clast (grain) size - the diameter of fragments or grains; angularity - the degree of edge or corner smoothness; sorting - the uniformity of grain size

Question 16

What are classifications of clastic sedimentary rock clast sizes?

Answer 16

Boulders, cobbles, pebbles, sand, silt, clay

Question 17

What are classifications of clastic sedimentary rock angularity?

Answer 17

Angular, sub-angular, sub-rounded, rounded; fresh clasts are usually angular, grain roundness increases with transport

Question 18

What are classifications of clastic sedimentary rock sorting?

Answer 18

Well-sorted and poorly sorted; more well-sorted the farther from the source you get

Question 19

Common nonclastic sedimentary rocks

Answer 19

Salt, coal, limestone, chert

Question 20

What does sedimentary structure refer to?

Answer 20

The layering of sedimentary rocks; Surface features on layers formed during deposition; Arrangement of grains within layers

Question 21

What do sedimentary structures provide evidence

about?

Answer 21

conditions at deposition!

Question 22

A single layer of sediment or sedimentary rock with a

recognizable top and bottom is called a…

Answer 22

bed.

Question 23

The boundary between two beds is called a…

Answer 23

bedding plane.

Question 24

Several beds together constitute…

Answer 24

strata.

Question 25

The layering in a sequence of beds is called...

Answer 25

bedding or stratification.

Question 26

Why does bedding form?

Answer 26

Bedding reflects changing conditions during deposition - changes in water depth, current velocity, climate, sediment; source and sediment supply causes bedding to form - these alter: Sediment composition, Grain size, Sorting, etc.