The correct option is 1 and 3 only.
Explanation
The mapping of the ocean floor reveals a complex topography including continental margins, abyssal plains, and mid-oceanic ridges. These features provide critical evidence for the theories of Seafloor Spreading and Plate Tectonics, particularly regarding the age of the crust and volcanic activity.
Statement 1 is Correct:
Abyssal plains are extensive, flat areas of the ocean floor found between the continental margins and mid-oceanic ridges. They are covered with fine-grained sediments like clay and silt, making them some of the flattest and smoothest regions on Earth.
Statement 2 is Incorrect:
Mid-oceanic ridges are an interconnected chain of mountain systems within the ocean basins. They are divergent plate boundaries where new oceanic crust is formed. Contrary to the statement, these ridges are zones of intense volcanic activity, with frequent eruptions occurring as magma rises from the mantle to fill the gap created by separating plates.
Statement 3 is Correct:
Scientific dating of rocks demonstrates a significant age difference between oceanic and continental crust. Rocks of the oceanic crust are much younger, with none being older than approximately 200 million years. In contrast, some continental rock formations are as old as 3,200 million years. This supports the concept that oceanic crust is continuously created at ridges and recycled at trenches.
Key Takeaway:
The ocean floor is dynamic; Mid-oceanic ridges are active volcanic zones where new crust is generated, ensuring that oceanic crust remains geologically young compared to the ancient, stable continental crust.