Plate tectonics (plate structure) is a coherent theory of massive crustal rearrangement based on the movement of continent-sized lithospheric plates, developed in the 1960's.

Earth's crust, the outermost shell, is made of a broad mixture of rock types which solidified billions of years ago, soon after the earth formed. It is not a solid "shell", it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

There are two kinds of crusts. The first is continental crust, which lies above the water. The second is oceanic. Oceanic crust is more active than continental, but it is thinner. The current continental and oceanic plates include: North American plate, Juan de Fuca plate, Cocos plate, Pacific plate, Carribean plate, Nazca plate, Scotia plate, South American plate, African plate, Antarctic plate, Arabian plate, Eurasian plate, Indo-Australian plate, Fiji plate, Caroline plate, and the Philippine plate. There are also smaller plates within these major plates.
Plates drift about the globe at about 1 to 10 cm per year, and over long periods of time, they change in size and shape. They may be added to, crushed together, or pushed back into the mantle. Plates can be 50-250 miles thick. Sea levels also changes over time, exposing more or less crust.

There are three types of plate movement: divergence, convergence, and lateral slipping.

In divergence, magma from the mantle wells up in the opening between  plates. This upward flow of molten material produces a continuous line of active volcanoes that spill out basalt onto the ocean floor. This is usually represented by an oceanic ridge. Divergence can also develop within a continent, resulting in a rift valley.

In convergence, plates moving in opposite directions meet, and the result of the collision normally is a vast crumpling of the edges as one plate subducts under the other. These are destructive because they result in removal of part of the surface crust. They are responsible for some of the most massive and spectacular of land forms: mountain ranges, volcanoes, and deep oceanic trenches.

In lateral slipping, two plates slip past one another laterally. The slippage edge is a great vertical fracture called a strike-slip fault. These boundaries usually form huge faults.
 
 

 The history of Earth contains a lot of changes in its climate. Evidence from rocks and fossils, like lush ferns and alligators found in what is now Siberia, or Dinosaur skeletons from north of the Arctic Circle show that temperatures on the Earth have generally fallen in the past 200 million years. Around 100 million years ago, the mid-Cretaceous climate was around 2
to 6 degrees Celsius (3.6 to 11 degrees F) warmer at the equator, and 20 to 60 degrees Celsius (36 to 110 F) warmer at the poles. This is due to the fact that the atmosphere levels were higher in the past. There are many theories that try to explain the changes in climate. We will be focusing mainly on the theory of continental drift.

Faster spreading rates of the continents would lead to faster rates of subduction of carbonate sediments and this, called weathering, in turn, would have led to increased rates of CO₂ production. There is evidence that indicates that the sea floor was spreading faster at the time of Pangaea's breakup than it has in any other time of geologic past. The main reason the atmospheric level was so high was from weathering. Weathering changes the Earth's surface by both chemical and
physical action. The unpolluted pH of rainwater is generally between 5 and 6. Rocks exposed at Earth's surface undergo chemical attack from this weak acid, one version of chemical weathering. Through chemical weathering, rocks
break down by the action of oxygen, carbon dioxide, and moisture, which absorbs organic acids from decaying animal and vegetable matter. Carbon dioxide readily dissolves in rainwater and sea water. Part of the rock is changed into soil and the rest is dissolved. Chemical weathering is most important in damp regions and physical weathering causes the most erosion in dry regions. The wind constantly wears away the surface of soft rocks. Water freezing, then thawing, also weather away at the rocks by cracking rocks near the surface. More weathering means more carbon into the atmosphere,
which means a higher level of heat. More CO₂ may also have been released by mid-ocean ridges themselves. Also,
since there was a higher sea level at that time, it would have meant that there was less land area available for weathering. This was caused by faster sea-floor spreading and the lack of polar ice. Equatorial continents should have been warmer and wetter than Earth as a whole (again assuming the planet's obliquity was low) and should have had higher rates of silicate weathering. This would have led to draw down of atmospheric CO₂, thereby cooling the entire planet. So, equatorial continents may actually cause global cooling.

Starting about 80 million years ago, Earth's climate began to cool. The initial decrease may have just been caused by a decrease in mid-ocean ridge spreading rates, which would lead to a reduction in atmospheric CO₂. The cooling trend accelerated around 30 million years ago during the Oligocene epoch in a way that does not really correlate with the spreading rate data. So, paleoclimatologists have searched for other explanations for the observed cooling. An interesting theory is that the carbonate-silicate cycle was perturbed by plate tectonics, but by a mechanism that differs from those
discussed previously.

This mechanism is mountain formation. Around 40 million years ago, the Himalayans and Tibetan Plateau were created. The Himalayas provided new erodable material on which silicate weathering could proceed quickly, and the Tibetan plateau created seasonal rainfall. These were the southeast Asian monsoons. The new mountains and rainfall provided for more erosion and weathering, contributing to the cooling of Earth. In addition, the smaller continents of Laurasia and Gondwanaland would have reduced the amount of land available to weather silicate rocks store
carbonate rocks, so the CO₂ sink would have been smaller.  A more detailed explination of this appears below.

There are other possible influences on the climate during this time of the Mid-Cretaceous Period.  The equator-to-pole temperature contrast during the Mid-Cretaceous Period was only 20 to 30 degrees C, as compared with 50 to 60
today. Part of this difference can be explained by the absence of polar ice at that time. Remember that ice cover has a strong, positive feedback loop. If we melted the ice caps, it would cause a large decrease in the albedo of
the polar regions which would cause them to warm significantly. Another influence on the climate was the thermohaline circulation of the oceans. At this point in time, they ran backwards: warm, but highly saline, deep water formed at low latitudes and welled up near the poles, where it then warmed the climate through evaporation. Unfortunately, nobody has yet
demonstrated that  this mechanism could work. Also, it has been thought that the tropical Hadley circulation extended further poleward than it does today. Hadley cells are very efficient at transporting heat. Bringing up the "Faint young sun" paradox, that  the sun gets brighter as it ages, it is also possible that as solar luminosity gradually went up, atmospheric CO₂ levels
gradually went down.
 
High levels of atmosphere may also have been caused by other factors than continental drift. One theory is that there have been variations in the amount of heat radiated from the sun. Another is that huge quantities of dust, put into the atmosphere during periods of intense volcanic activity, have decreased the amount of solar radiation reaching the Earth. Another is
that increased amounts of carbon dioxide, water vapor, and ozone--from volcanoes and from plants as well--have absorbed more of the sun's heat and thus lowering average temperatures. In a different aspect of warming and
cooling, the addition of carbon dioxide to the atmosphere as a result of burning more and more fossil fuels may cause global warming of atmosphere and oceans and extreme changes in climate, a problem we are dealing with
today.
 
 
 

120 to 90 Million Years Ago	100 Million Years Ago	60 Million Years Ago
-- Mid Cretaceous Period -- Much warmer than     today, especially at     the higher latitudes -- Continents were in     different places so    there were different    mountain chains and    shallow seas in the    places they are today	-- 5 to 15 degrees     Celsius warmer    than today-    believed to be    caused by the    different     continents'    arrangement	-- A warm equatorial    sea way split the     land horizontally -- Warm, swirling    currents brought    to all the oceans -- A cold current    circled the globe    when Australia     split from     Antarctica  -- The warm     equatorial sea ways    were blocked by    land as the    continents     continued to move, -- Oceans now     separated and     connected to the     polar latitudes by    huge cold current    swirls

To understand mountain building, you must first take alook at plate tectonics.  Plate tectonics is the theory that the Earth is made up of thin, rigid plates that move relative to each other.  The movement and the different type of movement causes a variety of effects that affect the Earth in a number of ways.  The type of movement that mountain building is most concerned with is convergent movement.  There are three types of convergent boundaries:  between two oceanic plates, between an oceanic and continental plate, and between two continental plates.  The types of boundaries that we must understand are boundaries between an oceanic and continental plate, and between two continental plates.  This will then shed some light as to how mountains were essentially built.

When a continental and oceanic plate converge, volcanoes tend to form.  Stress from the subduction of one plate forces the other to fold, which forms volcanoes.  The Andes was formed in such a way.  Volcanoes played an important role in affecting the climate of Earth.  The Pacific crustal plate began to slide under the South American plate and formed the Andes.  When two continental plates converge, again, subduction occurs.  The end result is usuyally a doubling of the land mass involved at the boundary.  Uplift, folding and wrinkling occur from the pressure exerted by the two plates an dmountains form.  The Himalayas were formed this way with the collision of India and Asia which is still occurring to this day.  This occurred during the end of the Mesozoic Era and on into the present day.

When a volcano erupted, it released large  amounts of carbon dioxide and water into the atmosphere.  While the carbon dioxide was largely used by plants for photosynthesis, sunlight broke down the water molecules into hydrogen and oxygen molecules that added to the growing ozone layer.  MOuntains play other important roles regarding climate.  Mfany block moisture dense clouds from passing, forcing them to precipitate on one side of the mountain while leaving the other side relatively dry.