This is an image of the eruption of Stromboli volcano.
Click on image for full size
Image from Dr. J. Alean, Eglisau, Switzerland
For more information, images and video about Stromboli volcano see Stromboli On-Line.


Lava is the word for magma (molten rock) which is extruded onto the surface of the Earth. Upon being released from the magma chamber and cooling, lava solidifies into rock. The term lava is used to describe active flows, solidified deposits, and fragments hurled into the air by explosive eruptions.

Lava comes in many different forms, among them are:

  • 'A'a - lava which has a blocky or spiny surface. A'a' is pronounced ah-ah because that is the sound someone will make if they unwittingly walk over a new flow which can appear very much like freshly tilled earth but still be tremendously hot.
  • Pahoehoe - Lava with a smooth, bulbous, or ropy appearance; its highly variable surface texture can lead to bizarre shapes.
  • Block lava - A solid rock fragment greater than 64mm in diameter which was ejected from a volcano or lava flow.
  • Bomb lava - Also known as volcanic bombs; lava fragments greater than 64mm in diameter which were ejected while partially molten.
  • Pillow lava - Lava released underwater forms elongate mounds or pillows.
Lava coming out the the volcano's mouth can flow at widely varying speeds. Lava flows normally move at speeds between 2/3 and 1/3 mi/hr. Lava in a tube or channel can flow quite a bit faster, usually topping out around 23 mi/hr. A normal walking speed is 2-4 mi/hr, while an athlete can run the 100 meter dash at just about 23 mi/hr. In other words, lava flows can usually be walked away from, but you should still be careful.

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