Lava flow is an outpouring of molten rocks on the surface. Lava flows are the most common volcanic feature on Earth.
Lava flows are distinct from each other:
- Pahoehoe lava flow,
- Aa lava flow,
- Blocky lava flow, and also
- Pillow lava flow.
- Sometimes Turbulent lava flow is also added.
Pahoehoe lava or Ropy Lava
Lava flows have a glassy, smooth, undulating or ropy surface. The term originated in Hawaii.
Pahoehoe is also known as ropy lava and it has several more varieties named entrail, festooned, filamented, sharkskin, shelly, etc.
InPahoehoe forms when the effusion rate is low and consequently the velocity of lava flow is slow. Pahoehoe lava flow is usually at least 10 times slower than typical aa lava flows.
Aa lava flows
Aa lava flows on the other handis a rubbly fragmental jagged, chunky lava, lava flow, usually basaltic in composition found in Hawaii and elsewhere. An aa flow contains relatively little gas and is a slow moving, flow 3 to 10 m thick. The surface of the flow cools and forms a crust while the interior remains molten. This hardened upper crust is broken into jumbled mass of angular blocks and kinkers. The gas in the flow forms bubbles and vesicles and makes the rock light and porous.Aa lava can be basaltic, andesitic, tephritic, etc.
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