Weathering, Erosion, and Mass Movement Flashcards Preview

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Flashcards in Weathering, Erosion, and Mass Movement Deck (47)
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1

Define weathering

physical breakdown and chemical alteration of rock at or near Earth's surface

2

What are the two kinds of weathering?

Mechanical and Chemical

3

Mechanical Weathering

physical forces breaking rock into smaller pieces

4

Chemical weathering

chemical transformation of rock into new compounds

5

True or False: Both kinds of weathering work simultaneously and reinforce each other?

True

6

True or False: Mechanical weathering increases surface area?

True

7

What is the relation between mechanical and chemical weathering

as mechanical weathering breaks rocks into smaller pieces, more surface area is exposed to chemical weathering

8

Types of mechanical weathering

-Frost wedging
-Sheeting/unloading
-Biological Activity
-Salt crystal growth

9

Frost wedging

-water that freezes in cracks enlarges the cracks
-lenses of ice increase in size as they attract liquid water

10

Unloading/Sheeting

-unloading leads to sheeting
-concentric slabs break loose when large masses of igneous rock are exposed due to erosion and glaciation.

11

How does an exfoliation dome form?

-continued weathering causes slabs to fall off and form a EXFOLIATION DOME

12

What are joints?

Joints are fractures produced by contraction during the crystallization of magma

13

Biological growth

-PLANT ROOTS grow into fractures in rocks, expanding cracks
-BURROWING ANIMALS move fresh material to the surface, enhancing mechanical and chemical weathering

14

Types of Chemical Weathering

-Dissolution
-oxidation
-hydrolysis
-spheroidal weathering

15

What is the most important agent in chemical wearthing?

Water

16

Three things about Dissolution

A small amount of acid in water is responsible for the corrosive properties
-CO2 dissolved in rain=carbonic acid
-Calcite (CaCO3) is particularily susceptible to weakly acidic solutoin

17

Three things about Oxidation

rust (iron oxide) forms when O2 combines with Fe
-water catalyses the rxn
-important in decomposing ferromagnesium minerals (olivine, pyroxene, hornblende, and biotite)

18

Two things Hydrolysis

-any rxn with water
-silicates (clay) decompose via hydrolysis

19

True or False: Clay minerals are the most abundant product of weathering

true

20

Spheroid weathering (3)

1) water penetrates jointed rocks
2) chemical waethering decomposes minerals and enlarges joints
3) rocks are attacked around the corners and edges, producing spherical shapes and fragments

21

What influences the rate of weathering

Rock Type and Climate
-silicate minerals weather in same order as Bowen's rxn series (Olivine --> pyroxine --> amphibole --> biotite etc)
-warm/moist climates enhance weathering
-cold/dry climates inhibit

22

Differential Weathering

uneven weathering due to different mineral composition

23

Examples of differential weathering

Soil
-portion of regolith that supports growth of plants

24

Define regolith

Mineral fragments that cover the surface of earth

25

Impact of human activity on soil

soil erosion (loss of topsoil)
-enhanced by deforestation and farming
soil conservation
-planting in patterns that follow contour of landscape reduces rate of water runoff
-grassed waterways between crops prevetns formation of gullies and traps soil washed from cropland

26

True or False: Weathering and erosion are slow processes (snail)

true

27

Define Mass Movement

movement of bedrock, rock debris, or soil downslope due to gravity
-ie. landslide

28

What is the main driving force of mass movement?

erosion agents (weathering, erosion etc)

29

Gravitational Driving Force

F(drive)=m*a=m*g

30

Friction and Cohesion RESISTING FORCE

F(res)= mu(fric)*mg*cos(theta)
F(res)=basal friction+internal strength