VOLCANOES: LAVA FLOW

EQ: What differences exist between types of lava flow?

LAVA FLOW Depends on:

TemperatureSilica content/Chemical compositionSlope of the landViscosity (the state of being thick, sticky,

and semifluid consistency)

TYPES OF LAVA Pillow Lava Pahoehoe (paw-hoey-hoey) A’a (ah-ah) Block Lava Rhyolite Lava (Rie-o-lite)

PILLOW LAVA Most abundant type of lava Large, elongated, interconnected lobes

that are elliptical or circular in cross-section

Important when looking at old rock sequences Indicates the presence of water

The underwater equivalent to pahoehoe Made mostly of basalt

PILLOW LAVA

PILLOW LAVA

PILLOW LAVA

PAHOEHOE 2nd most abundant type of lava flow. Smooth, billowy, ropy surface Relatively thin flow (few inches to a few

feet thick) Lava cools slowly, moves slowly Made mostly of basalt

PAHOEHOE

PAHOEHOE

PAHOEHOE

A’A Rough, jagged surface Aa lava flows tend to be thicker

compared to pahoehoe Cools quickly and moves fast Made mostly of basalt

A’A

A’A

A’A

BLOCK Block lava has a surface comprised of

large angular blocks. Block lava also refers to solid rock that

is ejected during an eruption.

BLOCK

BLOCK

BLOCK

RHYOLITE Rhyolite Lava is light in color, contains

69% silica or more. Rich in potassium or sodium.

RHYOLITE

RHYOLITE

RHYOLITE