Dynamic Earth Interlude B and Chapter 6

Physical weathering

: the mechanical breakdown of rock

Chemical Weathering

chemical reactions that break down
minerals, dissolving some, making new minerals from others

What is soil?

unconsolidated geologic material that has been
modified at Earth’s surface by weathering and the addition of organic material

What group of minerals is a product of weathering and common in soils?

Clay minerals  

Order of the five horizons in soil

O

A

E

B

C

What climate condition is necessary for the development of O and E horizons?

wet conditions

What are the three key nutrients in soil

N, K, P 

What and when was the dustbowl?

1930s, tornado alley, Midwest, great plains

Four classes of sediment/sedimentary rocks

Clastic

chemical 

Biochemical 

Organic

Clastic Sediment

pieces of rock or mineral grains ex. sandstone

Chemical Sediment

ions coming out of solution to create minerals ex. Rock-salt, rock-gypsum, evaporites)

Biochemical Sediment

organisms remove atoms from water/air/soil,
and the hard parts become sediments ex. limestones, cherts

Organic Sediments

plants remove atoms from water/air/soil, and plant matter becomes sediment ex. coal and oil shale

Lithification =

compaction + cementation

What are the grain size boundaries for sand/sandstone (in mm)?

0.0625 to 2mm

The concept of uniformitarianism

processes we see active today were active in the geologic past, and explain analogous characteristics observed in rocks

What is the basic unit of mapping sedimentary rocks?

Formation

Streams

Conglomerates, sandstones, and shales
– Channels in beds

Lakes

thin beds of shale

Rock salt and gypsum, arid environment

Swamps =

coal

Glaciers

Extremely poorly sorted boulder conglomerate

Dunes

Large Cross beds

Deep Oceans

bedded chert

Know two sedimentary structure that can be used to determine paleocurrent directions

cross bedding and ripples

Continental Rift Basins

Divergence -

Foreland Basins

convergent