Rocks Flashcards Preview

Physical Geography > Rocks > Flashcards

Flashcards in Rocks Deck (26)
Loading flashcards...
1
Q

What are the three types of rocks?

A

Igneous, Sedimentary, Metamorphic

2
Q

What is igneous rock classification based on?

A

Composition and texture

3
Q

What are the three basic compositional categories?

A

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

4
Q

How do you determine compositional category of igneous rock?

A

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

5
Q

What are the three textural categories of igneous rocks?

A

Crystalline, Glassy, Fragmental

6
Q

Finely crystalline

A

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

7
Q

Coarsely crystalline

A

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

8
Q

Porphyritic texture

A

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

9
Q

Glassy textures

A

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

10
Q

Fragmental textures

A

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)

11
Q

What are the two classes of sedimentary rock?

A

Clastic and Nonclastic

12
Q

Clastic sedimentary rock consists of…

A

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

13
Q

Inclastic sedimentary rock

A

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

14
Q

How are clastic sedimetary rocks created?

A

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)

15
Q

How do you classify clastic sedimentary rocks?

A

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

16
Q

What are classifications of clastic sedimentary rock clast sizes?

A

Boulders, cobbles, pebbles, sand, silt, clay

17
Q

What are classifications of clastic sedimentary rock angularity?

A

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

18
Q

What are classifications of clastic sedimentary rock sorting?

A

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

19
Q

Common nonclastic sedimentary rocks

A

Salt, coal, limestone, chert

20
Q

What does sedimentary structure refer to?

A

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

21
Q

What do sedimentary structures provide evidence

about?

A

conditions at deposition!

22
Q

A single layer of sediment or sedimentary rock with a

recognizable top and bottom is called a…

A

bed.

23
Q

The boundary between two beds is called a…

A

bedding plane.

24
Q

Several beds together constitute…

A

strata.

25
Q

The layering in a sequence of beds is called…

A

bedding or stratification.

26
Q

Why does bedding form?

A

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.