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 on the surface of the Earth. After being released from the magma chamber and cooling, lava hardens into rock. The term lava can describe active flows, cooled rock, and pieces hurled into the air during 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 walk over a new flow that can look like fresh dirt.
  • Pahoehoe - Lava with a smooth or ropy appearance that can lead to weird shapes.
  • Block lava - A solid rock chunk greater than 64mm in diameter which was ejected from a volcano or lava flow.
  • Bomb lava - Also known as volcanic bombs; lava chunk greater than 64mm in diameter which were ejected while still partially melted.
  • Pillow lava - Lava underwater forms long pillow-shaped formations.
Lava coming out the the volcano's mouth can flow at different speeds. It usually moves at speeds between 2/3 and 1/3 mi/hr. Lava in a tube or channel can flow quite a bit faster, speeding at a top speed of 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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