What are the different types of lava?

What are the different types of lava?

Lavas, particularly basaltic ones, come in two primary types: pahoehoe (pronounced ‘paw-hoey-hoey”) and aa (pronounced “ah-ah”). Both names, like a number of volcanological terms, are of Hawaiian origin. A third type, pillow lava, forms during submarine eruptions.

What is pahoehoe lava flow?

“Pahoehoe” is a Hawaiian word used to describe a lava flow with a smooth, ropy surface. Pahoehoe flows advance slowly, with small amounts of lava squeezing out of a cooler crust.

Why does basaltic lava flow faster?

Because of basalt’s low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move >20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns.

Which flows faster AA or pahoehoe?

Pahoehoe lava is smooth and can have a ropy, billowy appearance. A’a lava is much more ragged in appearance. It’s more viscous and moves faster, and it carries broken lava blocks called clinkers that cover the actual lava flow. Pahoehoe lava can sometimes turn into a’a lava when it encounters a steep slope.

How are magma and lava similar and different?

Magma is composed of molten rock and is stored in the Earth’s crust. Lava is magma that reaches the surface of our planet through a volcano vent.

Is magma hotter than lava?

Magma is hotter than lava, depending on how recently the lava reached the surface and if the magma and lava are from the same magma chamber below the…

What is the most explosive type of magma?

Pelean eruptions are considered violently explosive. Plinian – These eruptions result from a sustained ejection of andesitic to rhyolitic magma into eruption columns that may extend up to 45 km above the vent.

Which flows faster aa or pahoehoe?

Is pahoehoe a rock?

The term lava is also used for the solidified rock formed by the cooling of a molten lava flow. Mafic (ferromagnesian, dark-coloured) lavas such as basalt characteristically form flows known by the Hawaiian names pahoehoe and aa (or a’a).

What are the different sizes of phenocrysts?

There are a variety of sizes of phenocrysts from microphenocrysts to mega-phenocrysts and it is possible to find the entire range in a single rock. The size as noted above is largely due to chemical constituents available and the rate of cooling of the molten rock.

What is the difference between a phenocryst and a porphyry?

Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them. Phenocrysts often have euhedral forms, either due to early growth within a magma, or by post-emplacement recrystallization.

What happens during the formation of phenocrysts?

During formation of phenocrysts, the magma was cooled slowly giving time for large crystals to grow. Then, during late stages of lithification, the magma was rapidly cooled, forming smaller crystals as the matrix surrounding the phenocrysts.

What are plagioclase phenocrysts?

Plagioclase phenocrysts (white) and hornblende phenocryst (dark; intergrown with plagioclase) are set in a fine matrix of plagioclase laths that show flow structure. Rocks can be classified according to the nature, size and abundance of phenocrysts, and the presence or absence of phenocrysts is often noted when a rock name is determined.