Nope, glaciers. Baikal is an exception, because it is formed in the rift of two tectonic plates. The current crater is possible because the tundra is lots of f

Nope, glaciers. Baikal is an exception, because it is formed in the rift of two tectonic plates. The current crater is possible because the tundra is lots of frozen mud with gas in it. Gets warm, bubbles form, gas goes out. Edit: The gas is the result of biomass decaying. The cold had stopped the process for thousands of years but when the environment gets warmer, the bacteria activates and resumes the process.