Correct Option
The correct option is 1 only
Explanation
The global distribution of earthquakes and volcanoes is closely linked to plate boundaries. The depth of earthquake foci (shallow, intermediate, or deep) and the presence of volcanism depend on the type of interaction-divergent, convergent, or transform-occurring between tectonic plates.
Statement-wise Analysis
- Statement 1 is Correct: Mid-oceanic ridges represent divergent plate boundaries where new crust is generated. In these zones, the lithosphere is thin, and tectonic activity occurs near the surface. Consequently, the foci of earthquakes in mid-oceanic ridge areas are generally at shallow depths (less than 70 km).
- Statement 2 is Incorrect: The Alpine-Himalayan belt is a zone of convergence (collision between plates). While shallow earthquakes are common here, it is not characterized by shallow-seated earthquakes only. According to standard physical geography texts , this belt, along with the Pacific Rim, is associated with deep-seated and intermediate earthquakes, in contrast to the shallow events of mid-oceanic ridges.
- Statement 3 is Incorrect: The term "Rim of Fire" or "Ring of Fire" refers to the circum-Pacific belt (rim of the Pacific Ocean), which is home to the majority of the world's active volcanoes and earthquakes. The rim of the Atlantic Ocean is largely composed of passive continental margins and lacks this intense subduction-related volcanic activity.
Key Takeaway
Mid-oceanic ridges (divergent boundaries) are characterized by shallow-focus earthquakes, whereas convergent boundaries (like the Alpine-Himalayan belt and Pacific Ring of Fire) experience a range of depths, including deep-seated earthquakes.