The coincidence of the change in motion of the Pacific Plate with changes in plate motions between S. America and Antarctica shows how the motions of all the plates are interconnected - a change in the true motion of one plate leads to changes in the true motions of many others.
While these plate motions were taking place the effect on Antarctica was profound. By 34 Ma the climate cooled from the temperate conditions that previously existed. This was sufficient for glaciers to begin their advance, and was followed by a period of continued cooling until at about 20 Ma, glaciation was complete.
Even though the Drake Passage first opened at 50 Ma it was not until it opened to deep water at 34 Ma that glaciation really took hold. Today, the Antarctic Circumpolar Current is the strongest deep ocean current and its strength is responsible for the 'icehouse' climate that grips the planet. The opening of the Drake Passage had both a local and a global effect, initially cooling the climate of Antarctica from temperate to cold and ultimately playing an important role in the change from global 'greenhouse' conditions 50 Ma ago to the global 'icehouse' of today.
This example shows how plate tectonics, continental drift and the opening and closing of seaways can have a profound influence on both local and global climate. Throughout the Phanerozoic there were long periods when the Earth was much warmer than today - often called a 'greenhouse' climate - and other times when it was cold - called an 'icehouse' climate.
These cycles, like the Wilson cycle, occur over periods of Ma, reflecting the timescale of plate movements and the growth and destruction of oceans. Given the clear link between ocean circulation and climate, and the similar timescales of global climate change and plate motions, it is inescapable that one of the chief controls on long-term changes in the global climate must be plate tectonics. As you work through this course you will need various resources to help you complete some of the activities.
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Skip to main content. Could you imagine what would happen if some bit of land deflected the Antarctic Circumpolar Current? You don't have to imagine it all by yourself - go play with a paleoclimate animation and watch the climate change.
Look at it on a map. It matters where land is, and not just for the view. It shocked me to learn how intimately rocks are connected to climate.
We didn't talk about rocks when we discussed global warming in school. We talked about rainforests and fossil fuels and atmospheric gasses. There was some vague talk about how volcanoes could impact climate, but nobody mentioned the Deccan Traps , so I thought it was all small-scale, temporary stuff.
And nobody said diddly about actual rocks. They didn't talk about limestone and other carbonate rocks. Nobody bothered to tell me just how much CO 2 was stored up in those rocks, or said a word about how subducting carbonate rocks contribute to the CO 2 outgassing from volcanoes.
Boggles my mind, that does, and makes me look at the world in a whole new light. And, cherry on top, plate tectonics shaped human evolution. You know what I think surprises me the most about all this?
It's how interconnected all this world is, what an intimate whole all of the different scientific disciplines make. We break them down into categories for convenience, and sometimes forget that you can't have geology without chemistry, physics, biology, hydrology You can't understand one thing until you realize it's just a component of a much larger whole.
Nothing exists in isolation. It all relates. It didn't seem that way in school. Nobody ever taught it that way. So making these discoveries, seeing the way geology affects everything on earth, has been a tremendous surprise. More than that: a delight. It's delicious. During major explosive volcanic eruptions , large amounts of volcanic gas, aerosol droplets and ash are released. Ash falls rapidly, over periods of days and weeks, and has little long-term impact on climate change.
However, volcanic gases that are ejected into the stratosphere stay there for much longer periods. Volcanic gases such as sulphur dioxide SO 2 can cause global cooling, but CO 2 has the potential to cause global warming. In the present day, the contribution of volcanic emissions of CO 2 into the atmosphere is very small; equivalent to about one per cent of anthropogenic caused by humans emissions.
On a global scale, patterns of vegetation and climate are closely correlated. Vegetation absorbs CO 2 and this can buffer some of the effects of global warming. On the other hand, desertification amplifies global warming through the release of CO 2 because of the decrease in vegetation cover. A decrease in vegetation cover, via deforestation for example, tends to increase local albedo, leading to surface cooling. Albedo refers to how much light a surface reflects rather than absorbs.
Generally, dark surfaces have a low albedo and light surfaces have a high albedo. Ice with snow has a high albedo and reflects around 90 per cent of incoming solar radiation. Land covered with dark-coloured vegetation is likely to have a low albedo and will absorb most of the radiation.
Nowadays, most of what is on the Earth stays on the Earth; very little material is added by meteorites and cosmic dust. Large impacts like Chicxulub can cause a range of effects that include dust and aerosols being ejected high into the atmosphere that prevent sunlight from reaching the Earth. These materials insulate the Earth from solar radiation and cause global temperatures to fall; the effects can last for a few years.
A change in any one of these can lead to additional and enhanced or reduced changes in the others. For example, we understand that the oceans can take CO 2 out of the atmosphere: when the quantity of CO 2 in the atmosphere increases, the temperature of the Earth rises. This in turn would contribute to a warming of the oceans. Warm oceans are less able to absorb CO 2 than cold ones, so as the temperature rises, the oceans release more CO 2 into the atmosphere, which in turn causes the temperature to rise again.
A positive feedback accelerates a temperature rise, whereas a negative feedback slows it down. Discovering Geology introduces a range of geoscience topics to school-age students and learners of all ages. Climate is the pattern of weather of an area averaged over many years. We can only show whether climate change has occurred after decades of careful measurements and analysis. Temperature rises can affect agriculture, sea levels and the frequency of extreme weather incidents.
We can study past climate change by looking at the evidence in rocks, fossils and changes in the landscape.
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