Flashcards in Weathering, Erosion, and Mass Movement Deck (47)
physical breakdown and chemical alteration of rock at or near Earth's surface
What are the two kinds of weathering?
Mechanical and Chemical
physical forces breaking rock into smaller pieces
chemical transformation of rock into new compounds
True or False: Both kinds of weathering work simultaneously and reinforce each other?
True or False: Mechanical weathering increases surface area?
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
Types of mechanical weathering
-Salt crystal growth
-water that freezes in cracks enlarges the cracks
-lenses of ice increase in size as they attract liquid water
-unloading leads to sheeting
-concentric slabs break loose when large masses of igneous rock are exposed due to erosion and glaciation.
How does an exfoliation dome form?
-continued weathering causes slabs to fall off and form a EXFOLIATION DOME
What are joints?
Joints are fractures produced by contraction during the crystallization of magma
-PLANT ROOTS grow into fractures in rocks, expanding cracks
-BURROWING ANIMALS move fresh material to the surface, enhancing mechanical and chemical weathering
Types of Chemical Weathering
What is the most important agent in chemical wearthing?
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
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)
Two things Hydrolysis
-any rxn with water
-silicates (clay) decompose via hydrolysis
True or False: Clay minerals are the most abundant product of weathering
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
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
uneven weathering due to different mineral composition
Examples of differential weathering
-portion of regolith that supports growth of plants
Mineral fragments that cover the surface of earth
Impact of human activity on soil
soil erosion (loss of topsoil)
-enhanced by deforestation and farming
-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
True or False: Weathering and erosion are slow processes (snail)
Define Mass Movement
movement of bedrock, rock debris, or soil downslope due to gravity
What is the main driving force of mass movement?
erosion agents (weathering, erosion etc)
Gravitational Driving Force