Does pillow lava have a high or low viscosity?
In general, the more felsic the composition (richer in silica – resulting in an Intermediate composition), the larger the pillows, due to the increase in viscosity of the erupting lava.
What is pillow lava evidence of?
Seafloor Spreading Magma erupts on Earth’s surface as lava, which cools and crystallizes on the seafloor, forming rock. Because the lava erupts into water, it cools rapidly and forms rounded structures called pillow lavas.
How can the viscosity of lava be determined?
Temperature, composition, and volatile (gas) content largely determine the viscosity of lava. Temperature: The hotter the lava, the lower the viscosity (the thinner it is). The cooler the lava, the higher the viscosity (the thicker it is). The more mafic the lava (the less silica in it), the lower the viscosity.
Which lava is more viscous?
Viscosity of Magmas Thus, basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,0000 times more viscous than water. Rhyolitic magmas tend to have even higher viscosity, ranging between 1 million and 100 million times more viscous than water.
How does magma differ from lava?
Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth’s surface.
Why does pillow basalt form?
Pillow basalt is a volcanic igneous rock that forms when lava of basaltic compositionis erupted underwater. The rapid cooling of the lava by cold water on all sides forms the pillow-shaped bodies, which can then break open and extrude more of the hot lava from inside.
Where do you think this pillow lava erupted?
Pillow lava is commonly cited as the most abundant geologic landform on Earth’s surface. As described above, pillows form at low, though imprecisely known, flow rates. Pillow lavas have been observed while forming on the shallow submarine slopes of Hawaii, where subaerial lava flows enter the sea, and on W.
What is lava viscosity?
When it comes to liquids, viscosity is a measurement of how thick or syrupy it is. And the lava viscosity defines the size and shape of a volcano. Even though lava is 100,000 times more viscous than water, it can still flow great distances. When lava has low viscosity, it can flow very easily over long distances.
What is the viscosity of lava dependent on?
silica
Because of the role of silica in determining viscosity and because many other properties of a lava (such as its temperature) are observed to correlate with silica content, silicate lavas are divided into four chemical types based on silica content: felsic, intermediate, mafic, and ultramafic.
Does lava have high viscosity?
Even though lava is 100,000 times more viscous than water, it can still flow great distances. When lava has low viscosity, it can flow very easily over long distances. But most importantly, highly viscous lava is associated with explosive eruptions and dangerous pyroclastic flows.
Which type of lava is more viscous?
What is the composition of a pillow lavas?
Composition. Pillow lavas are commonly of basaltic composition, although pillows formed of komatiite, picrite, boninite, basaltic andesite, andesite, dacite or even rhyolite are known. In general, the more felsic the composition (richer in silica – resulting in an Intermediate composition ), the larger the pillows,…
How do you determine the viscosity of lava?
The viscosity of lava is determined partly by the amount of silica in the magma. Lava which contains a high percentage of silica is called felsic. If the lava contains around 50% silica, it is called mafic or basaltic. Felsic lavas tend to be more viscous than basaltic lavas.
What are the characteristics of a pillow volcano?
Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one metre in diameter. They form the upper part of Layer 2 of normal oceanic crust.
How does a pillow lava show it is still in orientation?
Pillow lava shows it is still in its original orientation when: Vesicles are found towards the top of a pillow (because the gas trapped as part of the rock is less dense than its solid surroundings).