Fissures

• Generally speaking, a fissure is a long and relatively narrow crack in the earth. Fissures may not breach the surface, but if they do, they will look like hairline fractures in the ground which may widen further depending on conditions. Fissures can cause a great deal of damage since they can widen under houses and buildings and destroy foundations and support frames. Fissures are also a problem concerning highways, which may be affected by forming fissures. While these geologic cracks can be formed by many different things, two of the most common are extensive ground pumping and the development of volcanoes.
  
  

Formation

• Fissures form in response to a stimulus. When people pump water from the ground for instance, it creates a suction that can cause underground stones to crack under pressure. This cracking may remain beneath the surface, but it can move upwards and open up the ground over time. Another cause for fissures forming is volcanic activity. The pressures from melting rock and gases in the earth can push up and lead to rock cracking and opening up into fissures. These fissures occasionally breach the surface, allowing gases and pressure out from deeper in the earth.
  
  

Geysers and Volcanoes

• Two of the most notable geologic formations that can come from fissures are volcanoes and geysers. Both of these form in a similar way. The pressure from below that comes from gases in the earth's crust, molten rock and other geologic functions can cause a fissure to form, making a crack in the earth. If steam and hot water escape through these fissures, they can reach the surface. If this happens with regularity, it can form a geyser. If, on the other hand, it's molten rock, or magma, that escapes through the fissure then it can eventually build up and become a volcano.