Figure 7.C Microscopic hard parts of radiolaria and foraminifera. This microscopic photograph has been enlarged hundreds of times. These organisms are sensitive even to small fluctuations in environmental conditions. (Photo courtesy of Deep Sea Drilling Project, Scripps Institution of Oceanography, University of California, San Diego.)

We know that the parts of the Earth system are related so that a change in one part can cause changes in any or all other parts. In this brief example, we see a case in which changes in climate and ocean temperatures are reflected in the nature of marine life. When the biochemical sediments produced by the microscopic organisms of the ocean floor are recovered, they can be used as substitute data to analyze the climates of the past. Reliable climate records go back a couple of hundred years ago, at the most. How do scientists know the climates and climate changes prior to this period? The obvious answer is that they must reconstruct the climates of the past from indirect evidence; that is, they must examine and analyze phenomena that respond to changing weather conditions and reflect them. An interesting and important technique for analyzing the history of terrestrial climate is the study of sediments from the ocean floor. Although ocean floor sediments are of many types, most contain the remains of organisms that once lived near the sea surface.

(the ocean-atmosphere interface). When these organisms near the surface die, their shells slowly deposit on the ocean floor, where they become part of the sedimentary record (Figure 7.C). One reason why ocean floor sediments are useful records of global climate change is that the amounts and types of organisms that live near the sea surface change as the climate changes. Richard Foster Flint explains this principle in the following way: It would be expected that in any area of the ocean / atmosphere interface the average annual temperature of the ocean surface water approaches that of the contiguous atmosphere. The thermal equilibrium established between the surface seawater and the air above it should mean that ... changes in climate should be reflected in changes in organisms living near the surface of the deep sea ...

If we remember that the ocean floor sediments of vast areas of the ocean consist mainly of pelagic foraminifera shells, and that these animals are sensitive to variations in water temperature, the connection between these sediments and climate changes becomes evident. Therefore, when trying to understand climate change, as well as other environmental transformations, scientists are using the enormous reservoir of data from ocean bottom sediments. The boreholes of the sediments collected by the drilling ships and other research vessels have provided invaluable data that have greatly expanded our knowledge and our understanding of the climates of the past (Figure 7.D).

Figure 7.D Scientists examine the sediment core test on board the JOIDES Resolution, the drilling ship of the Ocean Drilling Program. The ocean floor represents an enormous reserve of data referring to global environmental change. (Photo courtesy of the Ocean Drilling Program.)

A notable example of the importance of ocean floor sediments for our understanding of climate change is related to the clarification of the fluctuating weather conditions of the Glacial Period. The record of temperature changes contained in sediment core cores from the ocean floor has proved to be essential for our current understanding of this recent period in the history of the Earth.

Bibliography :

• Oceanographic studies of sediments .2012 Edward J. Tarbuck. Frederick K. Lutgens.
• Sedimentation of structures and sedimentary rocks .2001.jahsson f. Martinelli D.
• Sediment composites in deposits of sedimentary basins.2011. A, SWATH. H Caravelli.
• Sedimentary rocks in the oceans, studies of climatic behavior.2013. Marcella Granola