The surface soil must be loose but not too loose. If there is nothing to hold it down there will be constant dust storms. Volcanoes can make the soil loose and porous if the molten lava has dissolved gases in it. These are present on Earth because tectonic plates are always sliding over one another. This drags earlier ocean floors with their seashells and diatomaceous matter down into the mantle. The biological material, including dissolved carbon dioxide, later returns to the Earth’s surface in molten rock. If there were no dissolved gases the lava flows would produce a hard, impervious surface like that of Venus.