The Earth might swallow us whole. Scientists are raising the alarm over giant holes that have appeared around the Yamal Peninsula of Siberia. Last summer, three giant craters were discovered, and satellite imagery has since revealed another four, with some researchers fearing as many as 30 exist. Most experts believe the craters are caused by methane gas eruptions triggered by global warming. But studying gas emissions is risky, and scientists are calling for urgent investigations to bridge the gaps.