How does sea-floor spreading occur?
A. New materials are beaing added to the asthebosphere
B. Earthquakes break apart the ocean floor
C. Sediment accumulates at the area of spreading
D. Molten materials beneath Earth's crust rises to the surface
From Google:
seafloor spread·ing
nounGEOLOGY
noun: sea-floor spreading
the formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side.
Sea-floor spreading occurs as a result of the movement of tectonic plates on the Earth's surface. It is a geological process that happens at mid-ocean ridges, where the Earth's crust is being pulled apart. The correct answer to your question is option A. New materials are being added to the asthenosphere.
To further understand how sea-floor spreading occurs, we can consider the process of plate tectonics. The Earth's lithosphere is divided into multiple large plates that float and move on the semi-fluid layer below, called the asthenosphere. These plates interact along their boundaries, resulting in various geological phenomena.
At mid-ocean ridges, divergent plate boundaries exist, where two plates move away from each other. As the plates separate, magma, which is molten rock, rises from the underlying asthenosphere and fills the gap created by the separating plates. This magma solidifies and forms new oceanic crust, adding material to the seafloor.
This continuous process of magma rising, solidifying, and forming new crust leads to the spreading of the ocean floor. Over time, the newly formed crust pushes the existing older crust away from the ridge, creating a symmetrical pattern of crustal material on both sides of the ridge.
Option B, earthquakes breaking apart the ocean floor, is not the main cause of sea-floor spreading. Although earthquakes can occur along tectonic plate boundaries, they are a result of the stresses and movements associated with plate tectonics.
Option C, sediment accumulation at the area of spreading, is not significant in sea-floor spreading. Sediment primarily accumulates in areas where erosion, deposition, and the accumulation of organic matter occur, such as continental margins and deep-sea basins.
Option D, molten materials beneath Earth's crust rising to the surface, is a general description of volcanic activity, but it does not specifically explain sea-floor spreading. Volcanic activity can occur at subduction zones, where one plate sinks beneath another, or at hotspots, where plumes of mantle material rise through the crust. However, it is the process of magma rising at mid-ocean ridges that specifically leads to sea-floor spreading.
In conclusion, sea-floor spreading occurs because of the addition of new materials to the asthenosphere at mid-ocean ridges, where tectonic plates are moving apart.