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CHAPTER 4
學號:92625008
學生:莊竣皓
CO2 and Long-Term Climate
The historical materials in the past of the earth show that the earth temperature did not
change much for a long time. What mechanism allows the earth to own a constant
temperature?What is a thermostat ? Just like install a machine at inside a house, to regulate
the indoor temperature automatically, keeping the room temperature not down to
subcooling, or overheated. The greenhouse gas as function as a thermostat , Take the
Venus and make comparison with the earth relatively .The carbon contents of the Venus
and the earth are actually similar. Despite the fact that they store the carbon in different
ways, the Venus stores the carbon in the atmosphere, but the earth stores the carbon in the
rock stratum. To understand the exchanging situation of carbon stored in these places , we
must first understand the carbon circulation on the earth better . Carbon is stored in many
forms on the earth. A small part is stored in the atmosphere , ocean and plant. A slightly
larger part is stored in the soil. More are stored in the deep sea. Majority of the
remaining is stored in the rock stratum. Exchange of carbon among rock stratum is very
slow. The function of the carbon circulation is often the exchange between the surface and
interior of the earth. There are 2 different methods of the exchanging:
1. Carbon is usually released from under ground as the volcanos earth. CO2 in the rock
stratum are taken to the atmosphere , by geothermol power and hot spring.
2. CO2 is also released to the atmosphere by oxidation of organic carbon in sedimentary
rocks.
The earth has been existed for 4,550 million years. The carbon dioxide released to
atmosphere by volcanic eruptions enough to have greenhouse effects , and get not cause
the earth overheated . There must be ways to consume CO2 , to keep it in balance. When
we consider the carbon dioxide that the volcanoes offer for the atmosphere we must
consider the atmospheric reduction of carbon dioxide at the same time. The major
process that the carbon dioxide in the atmosphere is reduced is the chemical weathering of
the continent rock. There are two types of chemical weathering:
1. Hydrolysis: The main mechanism causing the CO2 reducing in the atmosphere is due
to hydrolysis losing CO2 to
1)formation of mode rock;
2)rainwater;
3)Carbon dioxide in the atmosphere ?
2. Dissolution
Hydrolysis: Most crust of the earth’s continent are composed of granites. Its
composition is the silicic acid saline. Carbon dioxide in the atmosphere dissolvd in the
rainwater and formed the carbonic acid. Rainwater dropped to the ground through
precipitation, turning into the groundwater. The carbonic acid in the groundwater will
corrode these silicic acids salinly slowly. Point of weathered rocks turned into clay and
mineral , and remain in the earth's continent crust. Chemically it can produce some ions,
including HCO3 - , CO32 - , H2SiO4,, H +. These ions can be transported to the sea, and stored
in the shells of the marine organisms via the biological courses.
Dissolution: If the object to dissolve is carbonic acid saline rock, the speed of
dissolution would be faster.
Three key elements related to chemical weathing are:
1.Temperature: The speed of chemical weathering is direct propontimal to temperature,
roughly the speed of weathering is doubled for each ten degrees of increasing in
temperature.
2.Rainwater: The rainwater plays the main role in hydrolysises . The more rainfall there is,
the more moisture content changes of the soil will be, and more carbon dioxide in the
atmosphere that will form the carbonic acid and enable weathering to go on.
3.Plant: Plant can absorb carbon dioxide from atmosphere and store it in soil through the
photosynthesis they carry on, and then form the carbonic acid with groundwater.
The biological process can influence chemical to weathering as well. The biological
process speed up the chemical weathering. The concept of chemical weathering is related
to the biosystem for: (1) carbon is a core of carbon dioxide circulation; (2 )plants offer
carbon dioxide to soil; (3)carbon dioxide is stored in the shell of the marine planktonic
organism in the form of calcium carbonate in the sea. It can form carbonic acid and
strengthen the hydrolysis. Biological process is very important to chemical weathering and
carbon circulation.
Based on what have been mentimed above, the earth has three thermostate controlling her
temperature:
1. Volcanism and geothermolly produced hot springs ;
2. Chemical weathering ;
3. Biological processes .
These three factors can control the earth is climate , keep the earth from turning into
subcooling or overheated and balance the carbon dioxide on the earth , maintain a warm
climate that enable mankinds to live on the earth.