the continental drift and seafloor spreading theory

Alfred L. WegenerIn 1910, Mr. Wegener formed a hypothesis which stated all the continents were once joined together in a giant landmass, he refer as the Super Continent or “PANGEA”

Geologist Alfred Wegener noticed similar rocks & fossil remains were found on continents which seemed to fit together, matching of glacial deposits, mountain ranges of the same age and Paleo-Climate zones.

The large landmass that included all of Earth’s present day continents

SHAPE OF THE CONTINENT

North America

South America

Africa

TRIVIA! Wegener was not the only

one to notice the fit of the continents.

1858: Antonio Pelligrini depicted Africa and South America connected.

He was one of the first scientists to publish maps depicting the apparent fit of the continents.

Similarity of Mountain Ranges-Rock Sequence

SAME ROCK, DIFFERENT RANGE Existing mountain ranges separated by vast oceans contain rocks of identical mineral content.

Matching of Glacial Deposits

Fossil Remains• Wegener mapped the locations of Fossils of several

species of plants and animals that could not swim.

It will be a long swim for Mesosaurus…

Paleoclimate Evidence

The Seafloor Spreading Theory

• Proposed in 1960 by a geologist named Harry Hess.

• Seafloor was moving outward Mid-0ceanic ridge, when Mid-oceanic ridge is pushed away toward the continents, more new oceanic crust is produced.

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• During subduction, oceanic crust is pushed against, and finally underneath, continental or oceanic crust.

• Subduction zones are often marked by overlying chains of volcanic islands called island arcs.

• Seafloor spreading results from convection in the mantle and lower crust.

• During convection, the hotter it is the more plastic material are brought up towards the surface while the colder it is the more sediment sink toward mantle.This convective forces break the ocean crust apart at the mid-ocean ridges forming a Rift Valley.Rift Valley is marked by high-angle faults, basaltic lavas, and high heat flows.

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• Ocean trenches develop over the subduction zone where subducted plate begins to bend and descend.

• Subduction causes contact and friction with the overlying plate which results in andesitic volcanoes and earthquakes.

• The youngest oceanic crust is formed at the crest of a mid-oceanic ridge, and the crust becomes older as they move away from the ridge.