New oceanic crust is formed at a constructive plate boundary

New oceanic crust is formed at a constructive plate boundary

• A. Sea-floor Spreading
• B. Rock
• C. Sial
• D. Sewage

Answer: (A)

Sea-floor spreading is the process by which new oceanic crust is produced as tectonic plates move apart at constructive boundaries. When the plates separate, magma from the mantle rises into the gap at mid-ocean ridges, erupts and cools to form solid rock, adding new material to the ocean floor and pushing the existing crust outward. This gradually widens the ocean basin over time. The other options aren’t processes for making new ocean crust: rock is simply the material formed, sial refers to a composition typical of continental crust, and sewage has no geologic relevance here.

Sea-floor spreading is the process by which new oceanic crust is produced as tectonic plates move apart at constructive boundaries. When the plates separate, magma from the mantle rises into the gap at mid-ocean ridges, erupts and cools to form solid rock, adding new material to the ocean floor and pushing the existing crust outward. This gradually widens the ocean basin over time. The other options aren’t processes for making new ocean crust: rock is simply the material formed, sial refers to a composition typical of continental crust, and sewage has no geologic relevance here.