A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.
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No,it is not important that it must be only fire it may be other source also
The last "hot house" or period of increased temperature occurred during the time of dinosaurs. The temperature in today's world is rising slowly but it is still miles away from the temperature that dinosaurs had to face during "hot house". I hope that the answer comes to your help.