Task: Question Answering
Input (English): Passage: The film adopts a linear plot.
Ice Quake is an action film about the Alaskan landscape, where there is a great threat that is going to affect the beautiful and gentle scenery. Under the permafrost, organic materials have been rotting for thousands of years and the compound is very deadly to the planet. As the permafrost thaws, underground volatile liquid methane and gases are created which causes a succession of violent and very destructive earthquakes. A family ends up going to this Alaskan landscape on the hunt for a Christmas tree, hoping to have fun, and unfortunately finds out firsthand how deadly this can be.
As they are exploring these mountains,  their dog runs away for an unknown reason and soon after there is an explosion of gas from underneath the ice that ends up causing an avalanche. The family has to run for their lives. The father takes charge and tries to lead them to safety when suddenly another tremor occurs. This time, it causes the ground to split open, creating a deep ravine dividing the family apart - the parents on one side and two children on the other. They cannot group back together as there is dangerous gas flowing out the ravine so the father tell them to go to the summit and wait for rescue. The children head up to top to then find out there is a storm on their way causing more concern. The younger brother suggests they keep moving until they can stop at a safe place
As this chaos is going on, the military based around the mountain are investigating the tremors. At first believed the tremors were being caused by earthquakes but then discover that there have been no tectonic movements and nothing has showed on the Richter scale. They then thought it could have been a volcano eruption causing this but also ends up to be false. It is a race against time to stop these harmful liquids and gases before it leads to a catastrophic explosion that threatens the planet. 
Question: What has melted to cause gas to come up from the ravine between the family?
Output (English): permafrost.