The oceanic crust is mostly made up of different types of basalt which extends how many kilometres beneath the ocean floor?

The correct answer is 5-10 km.

Key Points

• The oceanic crust is primarily composed of basalt, a dense, dark volcanic rock.
• The thickness of the oceanic crust ranges from 5 to 10 kilometers beneath the ocean floor, depending on its age and location.
• New oceanic crust is formed at mid-ocean ridges due to volcanic activity and spreads outward over time.
• It is thinner and denser than the continental crust, which is mostly composed of granite and is around 30-50 km thick.
• The oceanic crust is a crucial part of the Earth's lithosphere and plays a significant role in the plate tectonic cycle.

Additional Information

• Basalt
  • Basalt is a volcanic igneous rock that makes up the majority of the oceanic crust.
  • It is rich in minerals like pyroxene, plagioclase, and olivine, and has a high density compared to continental crust rocks.
• Mid-Ocean Ridges
  • These are underwater mountain ranges where new oceanic crust is formed due to tectonic plate divergence.
  • Examples include the Mid-Atlantic Ridge and the East Pacific Rise.
• Plate Tectonics
  • The oceanic crust is part of the Earth's lithosphere, which is divided into tectonic plates.
  • Plates interact at boundaries, leading to processes like subduction, where oceanic crust is pushed beneath continental crust, recycling it into the mantle.
• Oceanic vs. Continental Crust
  • Oceanic crust is thinner (5-10 km) but denser, while continental crust is thicker (30-50 km) but less dense.
  • The differences in composition and density play a key role in tectonic processes like subduction and mountain building.
• Seafloor Spreading
  • The process by which new oceanic crust is created at mid-ocean ridges and spreads outward.
  • This phenomenon provides evidence for the theory of plate tectonics, as observed through magnetic patterns on the seafloor.