The Solid Earth - Chapter 2: Weathering Flashcards
Disintegration and decomposition of rock or near the surface of the earth
Weathering
transfer of rock material downslope under the influence of gravity
Mass wasting
incorporation and transportation of material by a mobile agent, usually water, wind, or ice
erosion
As _____ breaks rock apart, it facilitates the movement of rock debris by erosion and mass wasting
Weathering
True or false: the natural processes that break apart a concrete sidewalk are different in nature from those that disintegrate rock
False
After millions of years of ___ and erosion, the rocks overlying a large intrusive igneous body may be removed, exposing it at the surface
uplift
Rocks will change gradually until they are once again in equilibrium with their new ____
environment
Mechanical and chemical weathering (do/do not) often work together
Do
When a rock undergoes this type of weathering it is broken into smaller and smaller pieces, each retaining the characteristics of the original material
mechanical
By breaking rocks into small pieces, mechanical weathering (increases/decreases) the amount of surface area available for chemical weathering
increases
What are the four important physical processes that lead to the fragmentation of rock?
Expulsion from unloading
Frost wedging
Organic activity
Thermal expansion
One of the most important processes of mechanical weathering is alternate freezing and ___
thawing
Water expands about ___ percent when it expands
9
The increase in volume in frozen water occurs because the molecules arrange themselves into a (straight line/open crystalline structure)
open crystalline structure
True or false: when water freezes it can exert a tremendous outward force
true
What is it called when rocks break into pieces after many freeze-thaw cycles?
frost wedging
Where is frost wedging most pronounced:? (Hint: this area goes through a daily freeze-thaw cycle)
mountainous regions
Large piles formed from sections of rocks that are wedged loose after frost wedging
talus slopes
When large masses of igneous rock are exposed by erosion, concentric slabs begin to (break loose/cool)
break loose
The process that produces the onion like layers that strip away in slabs in unloading
sheeting
In unloading, sheets begin to strip away because the pressure has (decreased/increased)
decreased
Fractures from unloading tend to develop (parallel/perpendicular) to the surface topography and give the exhumed igneous body a domed shape
parallel
Continued weathering eventually causes the slabs produced by sheeting to separate and spall off these large structures known as ______ domes
exfoliation
True or false: large rock slabs have been known to explode off the walls of newly cut mine shafts because of the reduced pressure
true
Fractures produced by contraction during the crystallization of magma and tectonic forces are known as ___
joints
Joints are important rock structures that allow ____ to penetrate to depth and start the process of weathering before the rock is exposed at the surface
water
The daily cycle of temperature change is thought to (weaken/strengthen) rocks
weaken
Which is true?
A. Heating a rock causes it to contract, and freezing a rock causes it to expand
B. Heating a rock causes it to expand, and freezing a rock causes it to contract
B
Which part of the shell is withstanding stress as the rocks expand and contract?
Shell
Scientists have debated the veracity of the thermal expansion explanation, and the plausible response they concluded is that rocks must be weakened by ____ _____ before they are broken down by thermal activity
chemical weathering
Plant roots in search of _____ and _____ grow into fractures, and as the roots grow they wedge the rock apart
Minerals
Water
This group of organisms further break down rock by moving fresh material to the surface where physical and chemical processes can more effectively attack it
burrowing animals
Decaying organisms produce ____ which contribute to chemical weathering
acid
This type of weathering involves the complex processes that alter the internal structures of minerals by removing or adding elements
chemical
___ is by far the most important agent of chemical weathering
water
Oxygen dissolved in water will ____ some materials
oxidize
When rocks containing iron-rich minerals _____, a yellow to reddish brown rust will appear on the surface
oxidize
Carbon dioxide (CO2) dissolved in water (H2O) forms ____ ____ (_____)
carbonic acid (H2CO3)
Rain dissolves some carbon dioxide as it falls through the ______, and additional amounts released by decaying organic matter are acquired as the water percolates through the soil
atmosphere
What very reactive hydrogen ion does Carbonic acid ionize to form?
H+
What is the very reactive bicarbonate ion formed when carbonic acid ionizes?
(HCO3-)
Because ____ ____ are the end product of weathering, they are very stable under surface conditions
clay materials
Clay materials make up a (high/low) percentage of the inorganic material in soil.
high
The abundant sedimentary rock ___ contains a high level of clay materials
shale
In the formation of clay minerals, some ____ is removed from the feldspar structure and carried away by groundwater
silica
Dissolved silica will eventually ____ to produce nodules of chert or flint, fill in the pore spaces between sediment grains, or be carried to the ocean, where microscopic animals will remove it to build hard shells
precipitate
The weathering of potassium feldspar generates a residual clay mineral, a soluble salt (potassium bicarbonate) and some _____ which enters into solution
silica
Quartz is very resistant to ____ weathering
chemical
Name the four ions silicate minerals yield when chemically weathered
Calcium
Potassium
Magnesium
Sodium
When angular rock masses are attacked by water that enters along joints, the rocks tend to take on a ____ shape
spherical
The process in which edges of rocks become more rounded
Spheroidal weathering
The addition of what increases size in spherical scaling?
water
The ____ weather in essentially the same order as their order of crystallization
Silicates
The optimum environment for chemical weathering is a combination of ___ temperatures and abundant ____
warm
moisture
This phrase means that rocks exposed do not weather at the same rate
Differential weathering
