The correct option is 2 only
Explanation
The question addresses the concept of Paleomagnetism and its role in validating the Sea Floor Spreading hypothesis. This involves analyzing the magnetic orientation of minerals (like magnetite) in ocean floor rocks relative to the Earth's magnetic field at the time of their formation.
Statement-wise Analysis:
- Statement 1 is Incorrect: As magma rises and solidifies at mid-oceanic ridges, it acquires the magnetic polarity of the Earth existing at that time. As the sea floor spreads, the newly formed crust moves away from the ridge in opposite directions. Therefore, rocks found at equal distances on either side of the ridge crest were formed simultaneously and exhibit similar magnetic polarities and ages.
- Statement 2 is Correct: The rocks forming currently at the mid-oceanic ridges record the Earth's present magnetic field, which is referred to as normal polarity. Consequently, the rocks closest to the ridge crest possess normal polarity. Reverse polarity is observed in adjacent, older strips of rock formed during geological epochs when the Earth's magnetic field was reversed.
- Statement 3 is Incorrect: The discovery of alternating magnetic stripes (magnetic anomalies) parallel to the mid-oceanic ridges provided the most robust evidence in support of the Sea Floor Spreading theory. This symmetrical pattern confirmed that new crust is generated at the ridges and pushes older crust outward, validating the mechanism of plate tectonics.
Key Takeaway:
The magnetic survey of the ocean floor reveals a zebra-stripe pattern of alternating magnetic polarities that is symmetrical around the mid-oceanic ridge, proving that the ocean floor spreads laterally from the ridge crest.