The mid-ocean ridges are elevated above the surrounding seafloor because Ridge rocks are hot and therefore of relatively less dense than adjacent cooler oceanic crust.
I hope this helps you! :)
The warm air that comes in Vietnam during the rainy season is most likely from the Pacific Ocean. In fact, tropical storms that pass over Vietnam form over the Pacific Ocean when the water warms up. The Pacific Ocean is at its warmest from June to November and the warm air and typhoons move inland over Vietnam.
To answer you question, The two main ingredients are Heat and coolness.
