Mid-ocean ridges are areas of rifting where two tectonic plates are diverging from one another. Deep-ocean trenches are formed at convergent plate boundaries where the more dense plate (usually the oceanic) subducts under the less dense (usually continental).

When lava gets erupted at the mid-ocean ridge axis it cools and turns into hard rock. As it cools it becomes permanently magnetized in the direction of the Earth’s magnetic field. This creates a symmetrical pattern of magnetic stripes of opposite polarity on either side of mid-ocean ridges.

What is the difference between mid-ocean ridges and trenches? Mid-ocean ridges occur at divergent plate boundaries. Trenches occur at convergent plate boundaries. The deep trenches occur where one plate is being subducted under another.

Along the mid ocean ridge, we can find the rift valley. A rift valley is formed on a divergent plate boundary, a crustal extension or spreading apart of the surface, which is subsequently further deepened by the forces of erosion.

Trench: very deep, elongated cavity bordering a continent or an island arc; it forms when one tectonic plate slides beneath another. Ridge: underwater mountain range that criss-crosses the oceans and is formed by rising magma in a zone where two plates are moving apart.

: an elevated region with a central valley on an ocean floor at the boundary between two diverging tectonic plates where new crust forms from upwelling magma.

divergent plate boundaries

Prominent examples of such mid-ocean ridge formations are along Africa, the Red Sea, in the USA where mid-ocean ridges have started to alter and newer ones have begun to form on account of the excessive heat.

There are two processes, ridge-push and slab-pull, thought to be responsible for the spreading seen at mid-ocean ridges, and there is some uncertainty as to which is dominant. Ridge-push occurs when the weight of the ridge pushes the rest of the tectonic plate away from the ridge, often towards a subduction zone.

As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. This rock (basalt) becomes a new part of Earth’s crust. Mid-Ocean Ridges. Seafloor spreading occurs along mid-ocean ridges—large mountain ranges rising from the ocean floor.

Terrigenous sediments

On the seafloor, sediments are thinnest near spreading centers (young seafloor) and thicker away from the ridge, where the seafloor is older and has more time to accumulate. – Sediment layers are thickest near the continents, the source of lithogenous material, and thinner farther out to sea.

Thickness in geology and mining refers to the distance across a packet of rock, whether it be a facies, stratum, bed, seam, lode etc. The concept of thickness came originally from mining language, where it was used mainly to indicate the workability of seams.

Sedimentary Rocks

Layering, or bedding, is the most obvious feature of sedimentary rocks. This Law of Superposition is fundamental to the interpretation of Earth history, because at any one location it indicates the relative ages of rock layers and the fossils in them. Layered rocks form when particles settle from water or air.

One evidence is rock layers specifically, what is called the geologic column. Basically, scientists have learned that rocks are stacked in layers containing fossils with the oldest fossils at the deepest layers, and the youngest, or most recent fossils, near the top.

remnant of a structure that may have had an important function in a species’ ancestors, but has no clear function in the modern species. Why are older fossils generally in deeper rock layers than younger fossils? the sediment has been building up on top of it.

Fossils are found almost exclusively in sedimentary rocks—rocks that form when sand, silt, mud, and organic material settle out of water or air to form layers that are then compacted into rock.

The type of rocks in which dinosaur fossils (and almost all other fossils) are found is called sedimentary rock. Sedimentary rock generally occurs as flat layers called strata (single layers called stratum).