At least 37 people have been killed, and more than a dozen injured on the Indonesian island of Sumatra after heavy rains triggered flash flooding and a cold lava flow from an active volcano, search and rescue officials said on Sunday. #indonesia #sumatra #volcano #flood #flooding #shorts Cold lava, also known as lahar, is a mixture of volcanic debris such as ash, sand and pebbles that flows down a volcano’s slopes during wet weather.