The theory of sea- floor spreading was introduced by Herny Hess in 1960s. Hess came with the idea

1950- Oceanographic vessels provided data on features of the ocean basin with lead to the discovery of mid-ocean ridges.

This lab uses earthquake data to construct profiles of two convergent boundaries: the Tonga Trench and the Peru-Chile Trench. Where two tectonic plates converge, if one or both of the plates is an oceanic lithosphere, a subduction zone will form. When crust is formed at a mid-ocean ridge, it is hot and buoyant meaning it has a low density. As it spreads away from the ridge and cools and contracts, or becomes denser, it is able to sink into the hotter underlying mantle. When two oceanic plates collide, the younger of the two plates, because it is less dense will ride over the edge of the older plate. The density of the

One evidence of this theory is molten material. Molten Material is magma erupting from mid-ocean ridges. Alvin the submarine found weird rocks shaped like pillows or toothpaste. This tells us this magma cools quickly underwater. Another type of evidence are magnetic stripes. Magnetic stripes are patterns in the ocean floor to prove Earth’s magnetic field has reversed itself in history. Scientist also looked at the “magnetic memory” of the rocks. Scientist drilled pipes through water to drill holes into the ocean floor. Scientists discovered that the older rocks were further away and younger rocks were closer. Those were the three types of evidence that scientist used to support the theory of Sea Floor Spreading.

The theory of plate tectonics was first developed by Alfred Wegener. He concluded that the continents seem to have a similar shape and could potentially fit together. This suggested that they were at one time joined together as part of 2 super continents called Gondwanaland and Laurasia was in the north. This theory was said to be proven by the discovery of fossilised remains of a mesosaurus that were found on the coasts of Brazil and Gabon. Sea floor spreading is another theory that supports the idea of plate tectonics; this theory discovered that rock is being formed under the ocean as a new sea floor. Sea floor spreading was shown in the Atlantic, where it is believed the Eurasian and North American plates are moving apart on a

The new volcanic material welling up into the void, which forms a ribbon of new materials and breaks down its center gradually, when the plates move apart from the axis of the mid-oceanic ridge system. Therefore, every separating plate accretes one half a ribbon of new lithosphere, and, thus, a new surface is added (Pitman, W.C, 2007). The process is continuous, and separation is always happening at the

The heavier oceanic plate is being pushed under and melted so that it will rise up the lithosphere as magma and gasses to cause an

To support the theory of continental drift is through topography, surveying the floors of oceans, charts of rock magnetism, and statistics on rock ages (Trefil & Hazen, 2010). At one time scientist believed that the deep ocean floors were flat; accumulating the sediment that progressively wore away from the prehistoric landmasses (Trefil & Hazen, 2010). However, they discovered steep-walled valleys and elevated highlands. This was evidences that just as the continents are transformed and are active, so to is the seafloor (Trefil & Hazen, 2010). The Mid- Atlantic Ridge, positioned in the central part of the Atlantic Ocean, is recorded to be the longest mountain range on this planet. Volcanoes, lava flow, and earthquakes are a source of

Cenozoic sedimentary rocks predominated to the west and east of the central mountain while plutonic rocks predominated in the peninsular ranges. The irregular contact between these geologic regions reflects the ancient topography of the area. The ancient oceanic crustal plate created an archipelago of a volcanic island. The former's subduction created immense volumes of magma. This resulted to the congealation of plutonic rock in the crust. The local rocks that existed before the tectonic forces uplifted, and erosion capped the deeply buried plutonic rocks that formed a steep and rugged mountains coastline, similar to that present one, which in the west coast of south America.

The creation of the Ring of Fire is very interesting too, it is the result of plate tectonics. These are huge slabs of Earth’s crust that fit together like the pieces of a puzzle. These plates can collide, stay apart, or move up right next to each other. The convergent plate boundaries are formed by plates colliding into each other. The heavier plates slide under the lighter plates causing a deep trench in the ocean floor, as we talked about earlier. If you went down into the ocean you’d be able to see a bunch of trenches in the ocean floor running parallel to corresponding volcanic arcs like the Ring of Fire. This allows islands and continental mountain ranges to be created. A divergent boundary is formed by

The youngest oceanic crust is located along the mid-ocean ridges where new crust is formed when the old crust is pushed away from mid – ocean ridges as a result of the seafloor spreading.

8.18 What explains the shrinking of ocean crust as the crust moves away from volcanoes?

However, if you travel away from the ridges you will encounter rocks with reverse polarity and then rocks of normal polarity which are followed by reverse polarity rocks, etc. Vine and Matthews observed that there were symmetrical bands of rocks with similar polarities on each side of every mid-ocean ridge. They hypothesized that the reverse polarized rocks formed at the ridges during the geologic past when the earth's magnetic field had reverse polarization. Their work provided rather elegant proof that the seafloor spreading actually occurs.

7. What is the relationship between plate tectonics and the ocean floor—seafloor spreading, for example?

Submarine volcanoes, mid-ocean ridges, and submarine canyons are all grouped into the marine geology systems. Underwater structures can actually be pretty useful to marine geologists, in 1930 studies found the seafloor to have all of the same physical features on land like mountains, volcanoes, canyons and more. The seafloor is estimated to be less than 2,000,000 year old, being a lot younger than landforms. The ‘age’ difference of the two makes marine geologists’ work a lot more fun to compare in finding the way rocks are built, how the sediments are compatible and finding an estimated location of natural disasters underwater.

After World War 2, the U.S. Office of Naval Research intensified efforts in ocean-floor mapping, leading to the discovery of the Mid-Atlantic Ridge to be part of a continous system of mid-oceanic ridges on all ocean floors, prompting Harry H. Hess to suggest the theory of sea-floor spreading. The oldest fossils found in ocean sediments were only 180 million years old and little sediment were accumulated on the ocean floor. Thus, he suggested that seafloors were no more than a few hundred million years old, significantly younger than continental land due to