Which material rises from cracks in oceanic crust?
dense crust
molten rock
continental crust
pillow-shaped rocks
The Correct Answer and Explanation is :
The correct answer is molten rock.
Explanation:
The oceanic crust is primarily composed of basalt, a dense, iron-rich volcanic rock that forms at mid-ocean ridges where tectonic plates are spreading apart. As the plates move, cracks form in the oceanic crust, allowing molten rock (magma) from the Earth’s mantle to rise up through these fissures. This molten rock is called lava when it reaches the ocean floor. When lava cools and solidifies, it forms pillow-shaped rocks. These distinctive structures are created due to the rapid cooling of lava when it comes into contact with the cold ocean water.
However, while pillow-shaped rocks are a result of this process, the initial material that rises from these cracks is molten rock, or magma, from the mantle. This molten rock then cools and solidifies, forming the pillow basalts.
To summarize the key points:
- Molten rock (magma) is the substance that rises through cracks in the oceanic crust.
- The lava, once cooled, forms pillow-shaped rocks, which are distinctive volcanic formations seen at mid-ocean ridges.
- The dense crust refers to the composition of the oceanic crust itself, and continental crust is not associated with the cracks in the oceanic crust, so these options are incorrect.
This process of magma rising and forming pillow basalts contributes to the creation of new oceanic crust and plays a major role in the theory of seafloor spreading. The phenomenon is key to understanding plate tectonics and the dynamic nature of the Earth’s surface.