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Why does gabbro have a higher chemical weathering rate than granite?
Wiki User
∙ 12y ago
Gabbro is mafic intrusive igneous rock and contains olivine, pyroxene, plagioclase and amphibole. These minerals are unstable at low pressure temperature conditions. In contrast, granite is felsic intrusive igneous rock and contains high amounts of quartz and orthoclase. Stability of minerals are increasing top to bottom in Bowen's Reaction Series.
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∙ 12y ago
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How can climate rates affect chemical weathering?
Humidity and temperature are the keys to chemical weathering (and to answer a previous poster, chemical weathering is a natural process, though human activity can affect it. Chemical weathering needs water, to act as a solvent and to transport corrosive ions so chemical weathering in arid climates, and in arctic climates (where water is frozen, and so not available) have little if any chemical weathering. Chemical processes are also (mostly) accelerated by higher temperature so the high humidity and high temperature of the tropics is the place where chemical weathering predominates . Contribution of humic acids from soils is also important, and the high rate of growth of plants in tropical climates is also a factor. While the solution of Limestones by acidified water is the most commonly quoted example, many minerals break down chemically, feldspar breaking down to clay minerals would be another important example.
Why might granite be pale in appearance?
Granite has a higher percentage of lighter colored minerals than do mafic intrusive igneous rocks.
How does the amount surface area affect the rate of weathering?
The surface area of a rock has a big affect on the rate of weathering. The higher the surface area of the rock in proportion to its overall mass will result in a quicker rate of weathering of the rock.
What factors determine the rate of weathering?
* Climate- Climate, which is usually measured in terms of temperature and moisture, can drastically affect the rate of weathering. High amounts of water and higher temperatures generally cause chemical reactions to run faster. Thus warm humid climates generally have more highly weathered rock, and rates of weathering are higher than in cold dry climates. Example: limestones in a dry desert climate are very resistant to weathering, but limestones in a tropical climate weather very rapidly. A high temperature and high amounts of water also controls vegetation which indirectly affects rate. Seasonality of precipitation affects rate to a degree. · Organisms (Biota) Animals- burrowing organisms like rodents, earthworms, & ants, bring material to the surface were it can be exposed to the agents of weathering.* Time- Weathering is a slow process. When we speak of time in a geologic sense, millions of years are often used as the units. The bedrock of Greenland has barely been weathered, and its age is over 3.5 billion years. The longer that a rock has been exposed to the weather, the faster it weathers. * Mineral Composition- All chemical and physical properties are determined by the mineral composition of the rock. Mineral composition is more important in determining the rate of chemical weathering. Those minerals that are most reactive with acids, water, and air are weathered at a more rapid rate. Mineral composition also affects physical weathering. Minerals that are soft (hardness lower thaan six) can be easily abraided and blasted. Slope - On steep slopes weathering products may be quickly washed away by rains. On gentle slopes the weathering products accumulate. On gentle slopes water may stay in contact with rock for longer periods of time, and thus result in higher weathering rates.· Porosity and faults and shears in materials Porous sediment equals better circulation and thus faster weathering process. Impermeable rocks will mean that no or little circulation will take place in rocks and weathering will be slower. Enhanced weathering rate occurs if faults and shears are present in rocks. * Exposure- Rock that is exposed to the atmosphere tends to weather much quicker. Bed rock that is covered by soil and vegetation may not weather as quickly. * Particle Size- The particle size of the material can affect the rate of weathering. The smaller the particle size, the faster it will weather. The more surface area that is exposed, the more it will weather.
Are basaltic igneous rocks lower in density than granitic rocks?
Granite is very much less dense than basalt. This is why the continental crust (mostly composed of granite) floats on Oceanic crust (made mostly of basalt). Granite is 70 % silicon. Where basalt is mainly pyroxene.
Why would basalt and gabbro generally have higher chemical weathering rates than rhyolite and granite?
The ferromagnesian minerals in the gabbro and basalt are subject to oxidation and chemical breakdown.
Does gabbro have a higher silica content than granite?
Gabbro has less silica than granite.
How does granite differ from gabbro in coloring and silica content?
Granite is lighter in color and higher in silicate mineral content.
Why does chemical weathering accure more quickly in a hot climate?
Chemical weathering occurs more rapidly in a hot, wet climate because chemical reactions speed up with increased temperature.
What increases the rate of chemical weathering of rock?
Chemical weathering can be increased if rainwater has is more acidic. Meaning it has a pH level higher than 5.5. Chemical weathering occurs quicker in warm and moist climates. :)
How does the rates of mechanical and chemical weathering might differ in the Congolese rainforest and the Siberian steppes?
Rates start at 69% and higher .
Factors that affect rates of weathering (climate)?
Two key factors affect the rates of weathering rock type and climate. Climate: is the single, most important factor that affects the rate of weathering. Chemical reactions occurs faster at higher temperatures, Warm climates favor chemical weathering, cold climates favor mechanical weathering(principally freezing and thawing), more moisture, or precipitation present, the more noticeable weathering.
What has a higher melting point iron or granite?
Granite has a higher melting point than iron.
How can climate rates affect chemical weathering?
Humidity and temperature are the keys to chemical weathering (and to answer a previous poster, chemical weathering is a natural process, though human activity can affect it. Chemical weathering needs water, to act as a solvent and to transport corrosive ions so chemical weathering in arid climates, and in arctic climates (where water is frozen, and so not available) have little if any chemical weathering. Chemical processes are also (mostly) accelerated by higher temperature so the high humidity and high temperature of the tropics is the place where chemical weathering predominates . Contribution of humic acids from soils is also important, and the high rate of growth of plants in tropical climates is also a factor. While the solution of Limestones by acidified water is the most commonly quoted example, many minerals break down chemically, feldspar breaking down to clay minerals would be another important example.
Why is granite easier to clean than limestone?
Granite and limestone are very different rocks. Granite is an igneous rock formed from magma. It contains many different types of minerals. See:http://en.wikipedia.org/wiki/Granite Limestone is a sedimentary rock. Although it may have many other minerals, it is primarily the mineral calcite, which has the chemical formula of calcuim carbonate. See: http://en.wikipedia.org/wiki/Limestone
What rock has more silica granite or basalt?
Granite is higher in silica than is basalt.
Why does weathering occur faster in higher elevations?
weathering occurs faster at high elevations because
