Tectonic–climatic interaction is the interrelationship between tectonic processes and the climate system. The tectonic processes in question include orogenesis, volcanism, and erosion, while relevant climatic processes include atmospheric circulation, orographic lift, monsoon circulation and the rain shadow effect. As the geological record of past climate changes over millions of years is sparse and poorly resolved, many questions remain unresolved regarding the nature of tectonic-climate interaction, although it is an area of active research by geologists and palaeoclimatologists.
Orographic controls on climate Depending on the vertical and horizontal magnitude of a mountain range, it has the potential to have strong effects on global and regional climate patterns and processes including: deflection of atmospheric circulation, creation of orographic lift, altering monsoon circulation, and causing the rain shadow effect.
One example of an elevated terrain and its effect on climate occurs in the Southeast Asian Himalayas, the world's highest mountain system. A range of this size has the ability to influence geographic temperature, precipitation, and wind. Theories suggest that the uplift of the Tibetan Plateau has resulted in stronger deflections of the atmospheric jet stream, a heavier monsoonal circulation, increased rainfall on the front slopes, greater rates of chemical weathering, and thus lower atmospheric CO2 concentrations. It is possible that the spatial magnitude of this range is so great that it creates a regional monsoon circulation in addition to disrupting hemispheric-scale atmospheric circulation.
The monsoon season in Southeast Asia occurs due to the Asian continent becoming warmer than the surrounding oceans during the summer; as a low-pressure cell is created above the continents, a high-pressure cell forms over the cooler ocean, causing advection of moist air, creating heavy precipitation from Africa to Southeast Asia. However, the intensity of the rainfall over Southeast Asia is greater than the African monsoon, which can be attributed to the awesome size of the Asian continent compared to the African continent and the presence of a vast mountain system. This not only affects the climate of Southeast Asia, but modifies the climate in neighboring areas such as Siberia, central Asia, the Middle East, and the Mediterranean basin as well. To test this a model was created that changed only the topography of current landmasses, which resulted in correlations between the model and global fluctuations in precipitation and temperature over the past 40 Myr. interpreted by scientists. It is commonly agreed upon that global climate fluctuations are strongly dictated by the presence or absence of greenhouse gases in the atmosphere and carbon dioxide (CO2) is typically considered the most significant greenhouse gas. Observations infer that large uplifts of mountain ranges globally result in higher chemical erosion rates, thus lowering the volume of CO2 in the atmosphere as well as causing global cooling. This occurs because in regions of higher elevation there are higher rates of mechanical erosion (i.e. gravity, fluvial processes) and there is constant exposure and availability of materials available for chemical weathering. The following is a simplified equation describing the consumption of CO2 during chemical weathering of silicates:
CaSiO3 + CO2 ↔ CaCO3 + SiO2 From this equation, it is inferred that carbon dioxide is consumed during chemical weathering and thus lower concentrations of the gas will be present in the atmosphere as long as chemical weathering rates are high enough.
Climate-driven tectonism There are scientists who reject that uplift is the sole cause of climate change and are in favor of uplift as a result of climate change. Some geologists theorize that a cooler and stormier climate (such as glaciations and increased precipitation) can give a landscape a younger appearance such as incision of high terrains and increased erosion rates. Glaciers are a powerful eroding agent with the ability to incise and carve deep valleys and when rapid erosion of the earth's surface occurs, especially in an area of limited relief, it is possible for isostatic rebound to occur, creating high peaks and deep valleys. A lack of glaciation or precipitation can cause an increase in erosion, but can vary between localities. It is possible to create erosion in the absence of precipitation because there would be a decrease in vegetation, which typically acts as a protective cover for the bedrock.
Models also suggest that certain topographic features of the Himalayan and Andes region are determined by an erosional/climatic interaction as opposed to tectonism. These models reveal a correlation between regional precipitation and a maximum topographic limit at the plateau margin. In the southern Andes where there is relatively low precipitation and denudation rates, there is no real extreme topography present at the plateau margin while in the north there are higher rates of precipitation and the presence of extreme topography. Another interesting theory comes from an investigation of the uplift of the Andes during the Cenozoic. Some scientists hypothesize that the tectonic processes of plate subduction and mountain building are products of erosion and sedimentation. When there is an arid climate influenced by the rain shadow effect in a mountainous region, sediment supply to the trench can be reduced or even cut off. These sediments are thought to act as lubricants at the plate interface and this reduction increases the shear stress present at the interface that is large enough to support the high Andes.
Volcanism
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