Continental Drift PDF
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This document provides an overview of the theory of continental drift, including evidence such as the fit of continents, matching rock types, and fossils found across oceans. The content also discusses the geological and paleontological evidence supporting this theory. It's a good resource for learning about the movement of tectonic plates on Earth.
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PLATE TECTONICS THEORY Continental drift Sea floor spreading CONTINENTAL DRIFT CONTINENTAL DRIFT 1. The fitness of continents and Continental Reconstruction Earth ~200 million years ago 1.1 Geometrical reconstruction of continents - Manually. - Math...
PLATE TECTONICS THEORY Continental drift Sea floor spreading CONTINENTAL DRIFT CONTINENTAL DRIFT 1. The fitness of continents and Continental Reconstruction Earth ~200 million years ago 1.1 Geometrical reconstruction of continents - Manually. - Mathematically on continental slope. (Bullard of Cambridge). (done by computer at 500 fathom= 927 m not at coastlines) which minimize the degree of misfit. Continental Drift: Evidence Tight fit of the continents, especially using continental shelves. It shows that there are: overlaps Examples: Iceland Niger Bahame platform gaps Examples: Iberian Peninsula Caribbean Sea The Continental Drift Hypothesis Proposed by Alfred Wegener in 1915. Supercontinent Pangaea started to break up about 200 million years ago. Continents "drifted" to their present positions. Continents "plowed" through the ocean crust. Breakup of Pangaea Continental Drift: Evidence Geographic fit of South America and Africa Rock types and structures match across oceans Fossils match across oceans Ancient glacial features Fold mountain belts. Matching Mountain Ranges Continental Drift: Evidence Glacial features of the same age restore to a tight polar Distribution (300-250M. Y. ago). 2. Euler's theory The movement of a portion of a sphere across its surface is defined by a single angular rotation about a pole of rotation (Euler pole of rotation). Atlantic Ocean formed before 200 M.y. in early Jurassic. It has Different poles of rotation at different ages: - 180 M.y. for North Atlantic - 130 M.y. for south Atlantic. - Before 80 M.y. the two parts have a unified pole of rotation. 3. GEOLOGICAL EVIDENCES FOR CONTINENTAL DRIFT 1- Fold mountain belts. 2- Age provinces 3- Igneous rock type (province) {Mesozoic dolerite dykes} 4- Stratigraphic sections (flora: glossopteris & gangamopteris) 5- Metallogenic provinces (manganese; iron ore; gold & tin) 1- Fold mountain belts. 2- Age provinces 3- Igneous rock type (province) {Mesozoic dolerite dykes} Continental Drift: Evidence 4. Stratigraphic sections (flora: glossopteris & gangamopteris and fauna ……..) 5- Metallogenic provinces (i. e.manganese; iron ore; gold & tin) Continental Drift _________ Wegener proposed the theory that the continents are drifting apart. This was supported by fossil and rock type evidence; also matching of coastline shapes. 4. PALEOCLIMATOLOGICAL EVIDENCES FOR CONTINENTAL DRIFT The study of climatic indicators in ancient rocks can be used as sedimentlogical indicator to infer their ancient latitude. 1- Carbonate and reef deposits: (with 28o latitude --warm water 25o-30o C). 2- Evaporates: hot arid conditions (high pressure zone) Evaporitation rate > sedimentation rate (Arid subtropical=10o- 40o latitude). 3- Red bed (arkosic sandstone, shale, conglomerates and hematite). They indicate: a- oxidizing agent b- Supply of iron c- Hot climate
