How are flood basalts formed?
Flood basalt is formed by an eruption or series of eruptions of large volcanic episodes that cover vast stretches of land or ocean floor with flows of mafic igneous rocks (basalt lava flows). Eleven distinct flood-basalt episodes have occurred in the past 250 million years, resulting in large volcanic provinces.
What are examples of flood basalts?
The most famous US example of a flood basalt province is the Columbia River Basalt province, covering most of SE Washington State and extending all the way to the Pacific and into Oregon. The Deccan Traps of NW India are much larger and the Siberian Traps are even larger than that (but poorly understood).
How do you identify flood-basalt?
Flood basalts have tholeiite and olivine compositions (according to the classification of Yoder and Tilley). The composition of the basalts from the Paraná is fairly typical of that of flood basalts; it contains phenocrysts occupying around 25% of the volume of rock in a fine-grained matrix.
Where can you find flood basalts?
In the USA we are familar with the Columbia River Flood basalts, which represent hundreds of black basalt lava layers which cover eastern Washington and parts of Idaho and Oregon (see map at right), erupted 15-17 my ago.
Do flood basalts have high viscosity?
One explanation for flood basalts is that they are caused by the combination of continental rifting and its associated melting. Then a mantle plume produces vast quantities of a basaltic magma. These have a low viscosity, which is why they ‘flood’ rather than form taller volcanoes.
What type of plate boundary is most associated with flood basalts?
Flood basalts On the continental plates at areas away from active convergence, the magmatism is confined to rift valleys and local hot spots. The volume of magma produced is minor in comparison to that generated at oceanic rises and at convergent plate boundaries. Flood basalts are the most common form of occurrence.
Are flood basalts effusive?
The largest known effusive eruptions on Earth have paved hundreds to thousands of square kilometers of its surface with basaltic lava. Erupting hundreds of lava flows over a period of a few million years, scientists refer to the resulting deposits as flood basalt and the areas covered as plateau basalt.
Is basaltic lava more viscous than andesitic lava?
In contrast to basaltic lava flows, andesitic lava flows have a higher SiO2 content of 52–62%, which makes the lava more viscous. Rhyolitic lava is high in SiO2 and has a lower iron and magnesium content than basalt lava.
Does basaltic lava flow easily?
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.
Are flood basalts associated with convergent margins?
Flood basalts The volume of magma produced is minor in comparison to that generated at oceanic rises and at convergent plate boundaries. Flood basalts are the most common form of occurrence.
Which of the following best describe how flood basalts form quizlet?
Which of the following best describe how flood basalts form? Flood basalts form as a result of an eruption above a mantle plume. Below is an image of the island of Hawaii. Kilauea, located on the Big Island, is a currently erupting volcano.
Is Mt St Helens effusive or explosive?
Helens can be confidently classified as an explosive eruption. The common image of red hot lava flowing down Kilauea and covering roads and houses is an effusive eruption. However, predominantly explosive volcanoes such as Mount St.
What happens to the magma in the Siberian Flood basalts?
Well, not quite. While the magmas are cooling in their chambers within the existing rocks of the Siberian crust, before eruption, a few crystals form. As they grow, these minerals trap tiny droplets of the liquid magma around them within their crystal structure.
Where do flood basalts occur on the Earth?
Flood basalts occur in the middle of plates. Though there are no flood basalts erupting on Earth today, we see the many thin layers of lava of past eruptions stacked up in western India, Brazil, Antarctica, the Columbia River, and elsewhere.
How much ozone was destroyed by the Siberian Flood?
Work by Ben Black, Jeff Kiehl, Jean-Francois Lamarque, and Christine Shields at the National Center for Atmospheric Research showed that the halocarbons released by the Siberian flood basalts would have destroyed as much as 70 percent of the Earth’s ozone, worldwide.