Overview of Module 5 – Earth’s Processes

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Overview of Module 5: Earth’s Processes

Since the formation of the Earth, both the atmosphere and lithosphere have been continually changing, each influencing the other. The processes of plate tectonics, together with the formation of water and the introduction of life, have further contributed to these changes. All three, in combination, have altered and continue to alter both the atmosphere and lithosphere.

With the discovery of fossils, it became possible to develop the geological timescale and to determine when mass evolution and extinction events occurred. Both were and are strongly influenced by the phases of the plate tectonic supercycle, which has a significant
effect on climate. This knowledge gives us new information about climate and natural cycles of change.

Investigate the evidence for the origin of organic molecules on the Earth, including:
➔ Urey and Miller’s experiments
He used a mixture of chemicals, such as CH4, NH3, H2, H20, along with generated electrical sparks to simulate lightning, in the atmospheric chamber and let the apparatus run for a week. After a while, when miller analysed the chemicals in the water, he found a large variety of amino acids, also known as organic molecules are the building blocks for proteins. These proteins are structural components in cells and they control the thousands of metabolic processes that take place in cells. Miller showed that in the right conditions, organic molecules can form from inorganic ingredients; and it has been shown that the building blocks of DNA, carbohydrates and other organic molecules can also be formed in this manner. Whilst it is important to note that this experiment did not prove how life evolved, it provides a plausible theory by which it may have occurred.

➔ Communities around Black smokers
Life additionally, could have formed on the ocean floor near hydrothermal vents. These sources of very hot water from deep in the Earth may carry sulphides which react with chemicals in the seawater to produce “black smokers”. Black smokers are defined as hot water from deep in the earth which is rich in methane and ammonia which in the tight conditions can react to produce amino acids and other organic molecules. Clay particles also occur near these events and can catalyse the necessary reactions. This would need to be in a region between the very hot water from the vent and the very cold water of the oceanic floor

● Researchers such as Günter Wächtershäuser have proposed that life began in submarine hydrothermal vents. His theory requires a cycle of chemical reactions to take place, releasing energy in a form that allows the exploitation by other processes. To account for a hydrothermal origin of life, amino-acid synthesis has been proposed to occur in the Earth’s crust, where they were consequently injected into cooler water with hydrothermal fluids. The presence of clay minerals at these lower temperatures may have promoted the genesis of amino acids such as peptides and protocells, and hence the first origins of life