CLIMATIC CHANGE

1. CLIMATIC CHANGE A Geomorphologic View Prof. L.A.Dei

2. Processes • Geomorphologic processes involve a certain amount of movement, either laterally or vertically. • This movement is a change of place or position and represents a certain quantity of work which consumes energy. • The earth’s surface operates and uses energy continuously throughout geologic time, but it should not be thought of as a perpetual mobile.

3. The Time Factor • It steadily consumes energy and must be recharged so that it does not cease to operate. • This energy is constantly supplied by the prevailing regional or local climate. which varies through time. • The earth’s magnetic field is weakening very fast in the Bermuda triangle and in south Japan causing serious distortions in global oceanic and atmospheric circulation. Gravity anomalies along the coast of Japan and their association with ocean circulation, e.g. El Nino etc

4. Our Changing Climate • The earth’s surface operates and consumes energy and must be recharged so that it does not cease to operate. • In reality climate is always changing ,just as the controlling influences are never quite the same, and the word normal is correspondingly misleading. It is strange to consider a particular type of climate as normal, whilst others are abnormal or accidental,

5. Climatic Variation Through Geologic Time • Climatic variation is a normal phenomenon associated with our planet since Precambrian times. • Geomorphologic processes and forms have correspondingly varied through geologic time. • The result is the formation of landforms of varied climatic origin worlwide.

6. Examples of Global climatic Change • The cold Cambrian climate in Europe gave way to warmer conditions until the Permo-Carboniferous glaciations disrupted these warm conditions, • Between Triassic and Pliocene, warmer climates replaced the cold of the preceding era until the Plio-Pleistocene glaciations in Europe and high altitude areas.

7. Some Anomalies of the Change • The preponderance of warm climates in the past is striking as there were varying degrees of warmth. • For example the North American Silurian was warm and dry and corals flourished and built reefs as far north as Greenland. • Triassic deposits were produced by the ferruginisation of their constituent grains associated with lack of vegetation.

8. Quaternary: Most Recent Climatic Change • The Quaternary belongs to the Cainozoic which started about 50 million years ago. • Miocene - Flowering plants about 13 million years ago. Pliocene- Mammals about 9-10 million years ago. • Holocene or Pleistocene - Modern man about 2-3 million years ago in. Pleistocene ended 10 to 15000 years ago. Time is too short, geologically, to complain about climatic change which is normal.

9. Quaternary In The Tropics • Leakey(1936) observed the following Pluvial conditions in the tropics: Kageran, Kamasian, Gamblian Makalian,Nakuran. • These conditions seem to tally with the European glacial conditions, namely Wurm, Riss Mindel and Gunz. • Glacial stages lasted from about 30,000 to 100,000 years. These tally with Pluvial conditions in the tropics.

10. Evidences of Pluvial Conditions In Africa • North Africa was green, fertile and populous and had large ostrich population • The steep-sided wadis now dry had permanent streams • Prehistoric Niger flowed northward to the Mediterranean. • Lakes, river terraces and travertine existed in Morocco. • The ancestral Nile was a mighty fast-flowing river with many tributaries

11. Evidences Of Pluvial Conditions In Asia • The main terrace (400m) of the Dead Sea corresponds with a vast lake,250 km long and 50km broad. • Pluvial lakes covered many inland basins of Syria, Iraq, Saudi Arabia, Iran, Afghanistan and many places of the dry Middle East • Fossil lateritic soils, forests, tin - bearing deposits and others all prove pluviation.

12. Evidences Of Pluvial Conditions In North America. • The Great basin in Nevada, Utah, Oregon, California and New Mexico, has widespread evidence of former moisture in basins similar to modern playas and having been formed by leaching and wind deflation during the Pleistocene. • Sixty-eight lakes lay within the Great Basin.

13. Evidences Of Pluvial Conditions In South America • Evidences of river terraces and powerful springs existed in the Atacama and North Chile • There is proof of lakes now considerably shrunken or completely vanished, such as salt lakes of Argentina and Bolivia, including the vanished Lake Minchin or Lake Poopo, Lake Morkill in Cuzco basin of Peru.

14. Pluvial Evidence In Australia • In Australia, heavier precipitation occurred in the inland basins. Thus numerous lakes lay around Lake Eyre which covered 100,000 sq.km and in the Flinder’s Range and in the Flinder’s Range and in the south-east. • A rainforest flora spread over the continent, even to its central parts- remnants survive in a few spots.

15. Other Examples • In Ghana river piracy had taken place due to heavy rainfalls during the Pluvial periods. This benefited the Volta, Pra, Pawmpawm and other rivers. • The Elmina sandstone was deposited under semi-arid conditions, explaining why its constituent feldspar remains intact along the beach zone.

16. Other examples cont’d • There are varve deposits in Ajua shales indicating a period of extreme cold in this part of the world. Further the gold –rich Tarkwaian rock of Ghana bear similarities to the gold-rich banket ores of South Africa. This is explained by the fact that the agent of deposition, a mighty primordial river, was responsible for their deposition.

17. Conclusion • Modern man has been in existence only 2-3 million years. • Climate has changed in the past for several hundreds of millions of years in a natural environment without the interference by man-no green house effects, carbon monoxide emissions, no aircrafts, no refrigerators, no air conditioners, no space crafts or man-made satellites. The change then was extra-terrestrial and must be accepted as such. The climate will continue to change according to the laws of nature irrespective of man’s frantic efforts to try to solve the problem.

18. End • Thank You