What are the 2 different types of weathering?
Mechanical, Chemical
Definition of Mechanical Weathering
Any process whereby rocks are broken and reduced in particle size with no change in composition.
Disintegration
Any process by which a rock is broken into smaller pieces with no change in composition.
Definition of Chemical Weathering
The decomposition of rocks and minerals by the processes of dissolution, oxidation, and carbonation/hydrolysis.
Dissolution
The dissolving of a solid by a solvent.
Oxidation
Chemical reaction by which compounds combine with oxygen. (Example: Iron)
Hydrolysis
Chemical reaction involving water.
Carbonation
Process of chemical weathering whereby rocks and minerals containing calcium, magnesium, potassium, and iron are transformed into carbonates, or bicarbonates, by reacting with carbonic acid. (Example: Dissolved CO2 )
Mechanical Weathering
Disintegrates Rocks
Mechanical Weathering
Physical break-down of rocks into smaller chunks/ particles.
Chemical Weathering
Chemical break-down of minerals in rocks
Clay, Quartz, Feldspar, Iron Oxides
Products of chemical Weathering
Physical Weathering
Agents are: Water, Plants, & Animals
Hydrolysis / Carbonation
Very important process for the breakdown of feldspars into clay minerals.
Products of Weathering
Regolith, & Soil
Regolith
The layer of unconsolidated material accumulated above bedrock. The loose material atop the bedrock; it combines the products of both mechanical and chemical weathering and consists primarily of rock fragments, clay minerals, and quartz.
Soil
The portion of the regolith that supports plant life out doors.
First in a series of processes collectively called Erosion
Weathering
Erosion
The wearing away of any part of Earth's surface by natural processes. Where the Earth's surface is loosened, dissolved, and worn away, and simultaneously moved from one place to another, by natural agents.
Soil
A major end product of the process of weathering.
Weathering
Any reaction between a rock surface and the agents of the atmosphere.
Weathering
Process whereby rocks either disintegrate or decompose.
Decomposition
Any process that results in either a partial or complete change in the mineral and elemental composition of the original rock.
Bases for the two modes of weathering
Disintegration & decomposition
Frost Action
Most common mechanical weathering process. Result of a special property of water. Water expands when it converts from a liquid to a solid. Expanding ice will break the strongest rock.
Freeze That cycle
Temperature rises and the ice melts, more water enters the expanded crack and penetrates deeper into the rock. The next freeze opens the crack even further. Each cycle enlarges the crack, eventually separating the block of rock from the main rock body.
Talus
An accumulation of rock fragments at the base of a steep slope such as a cliff or road cut. Can often be an end product of frost action.
Exfoliation
A mechanical weathering process by which concentric layers of rock of various thicknesses are removed from a rock mass. (Like the removal of layers from an onion.)
Play major roles in all processes of chemical weathering
Water and Temperature. Very few chemical reactions go on w/o the intervention of water.
Limonite
Common product of oxidation (Chemical Weathering), which is a variable mixture of iron oxides.
Oxidation in ferromagnesian minerals and mafic rocks
Oxidation is especially important in the decomposition of ferromagnesian minerals and mafic rocks, because they contain iron (Fe) which most readily reacts with oxygen.
Iron oxides produce by chemical weathering are largely responsible for the ___ of most sedimentary rocks.
Color
Oxidation of the sulfide minerals always results in the formation of ____.
Acid
____ dissolves more materials than any other known solvent.
Water
Carbon dioxide is an important gas that dissolves in water, which reacts to form ____.
Carbonic Acid
Carbonation
The reaction between a mineral and dissociated carbonic acid.
Limestone
Important example of rock dissolution by carbonation (chemical weathering)
Carbonation / hydrolysis of almost any common silicate mineral except olivine and quartz will
reduce the original mineral to clay minerals and a variety of soluble materials that are carried off in solution.
Rates of most chemical reactions increase with an increase in______
Temperature
Minerals that crystallize first at the highest temperatures will show the ______ rates of chemical weathering.
Highest
Minerals that crystalize lase at the lowest temperature rates will show the ___ rates of chemical weathering.
Lowest
Mineral that is the most resistant to chemical weathering.
Quartz
Major agent of physical/ mechanical weathering is ___
Freezing water
Oxidation primarily involves the element___.
Iron
Water is such an effective agent of chemical weathering because it:
Contains dissolved oxygen and carbon dioxide.
Which of the following igneous rocks would you expect to have the fastes rate of chemical weathering? Granite, Rhyolite, Basalt, or Granodiorite.
Basalt
Which of the following minerals would you expect to weather at the fastest rate? Olivine, Quartz, albite, or Orthoclase.
Olivine
The major mineral that forms by the chemical weathering of most silicate minerals is __.
Clay
The total accumulates products of weathering refers to
Regolith
Which area would frost wedging be most effective?
Regions of temperate, humid climate.
The process by which nearly all rock-forming silicate minerals decompose.
The chemical weathering process of carbonation/ hydrolysis.
Which igneous rock would weather chemically as the slowest rate? Gabbro, Basalt, Peridotite, or granite.
Granite
Most important agent of physical weathering is?
The freezing and thawing of water
The atmospheric gas most responsible for the chemical decomposition of most silicate minerals is?
Carbon Dioxide
Mafic rocks will weather ___ than felsic rocks.
Faster
Of the major rock-forming silicate minerals, those that exhibit the fastest rates of chemical weathering are_
Those that crystallize at the highest temperatures.
Why is Quartz the most chemically stable mineral?
It does not react w/ either dissolved oxygen or carbon dioxide.
Nearly all processes of weathering require___
Water
The two atmospheric gases responsible for chemical weathering are ___ and ___.
Carbon dioxide, Oxygen
The only rock-forming mineral that undergoes decomposition by the process of dissolution is __
Calcite
Mineral produced by the chemical wreathing of nearly every rock-forming silicate mineral is_.
Clay minerals
Acid rain" is acidic because of its content of ___.
Carbonic Acid
The process whereby layers of rock are removed by various process of physical weathering is called___
Exfoliation or spalling
Metastable
Minerals such as gold, graphite, and diamonds that survive all processes of weathering. Minerals that can exist indefinitely at Earth's surface.
Sheeting
The kind of exfoliation that is associated with exposed igneous rock bodies.
Spalling
The removal of rock in sheets or flakes
Dissolution
The process of dissolving
Disintegration
The physical reduction in particle size of rocks
Exfoliation
The removal of rock in concentric layers
Trace Element
Elements with crustal concentrations less than 1 weight percent.
Major agents of physical weathering.
Frost wedging, plant roots, and animals
Why does Ice float on water?
Because it is less dense