Trenches, accretionary wedges (prisms) and volcanic or island arcs are key surface features produced by subduction. A subduction zone is the entire area of subduction between the trench and the volcanic arc.

These plates collide, slide past, and move apart from each other. Where they collide and one plate is thrust beneath another (a subduction zone), the most powerful earthquakes, tsunamis, volcanic eruptions, and landslides occur.

Deep trenches are features often formed where tectonic plates are being subducted and earthquakes are common. As the sinking plate moves deeper into the mantle, fluids are released from the rock causing the overlying mantle to partially melt.

Several types of evidence supported Hess’s theory of sea-floor spreading: eruptions of molten material, magnetic stripes in the rock of the ocean floor, and the ages of the rocks themselves.

Harry Hess’s hypothesis about seafloor spreading had collected several pieces of evidence to support the theory. This evidence was from the investigations of the molten material, seafloor drilling, radiometric age dating and fossil ages, and the magnetic stripes.

Seafloor spreading is a geologic process in which tectonic plates—large slabs of Earth’s lithosphere—split apart from each other. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks.

Explanation: Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.At a spreading center, basaltic magma rises up the fractures and cools on the ocean floor to form new seabed.

subduction zones

Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized “stripes.” These stripes hold a record of reversals in Earth’s magnetic field. The rock of the ocean floor contains iron. The rock began as molten material that cooled and hardened.

Tectonic plates, the massive slabs of Earth’s lithosphere that help define our continents and ocean, are constantly on the move. Plate tectonics is driven by a variety of forces: dynamic movement in the mantle, dense oceanic crust interacting with the ductile asthenosphere, even the rotation of the planet.

Earth’s tectonic plates are in constant motion. Their movement is driven by heat within the Earth. This causes hot material within the Earth to rise, until it reaches the surface where it moves sideways, cools, then sinks. This circular motion is called convection.