When subduction-derived magma encounters thick continental crust, it can either penetrate the crust and produce a volcanic arc or pond beneath the surface. A recent study published in Nature Geoscience has found that when this happens, the magma’s temperature drops, and its viscosity increases. This is due to water diffusion within the rock which lowers its melting point by about 100 degrees Celsius.
A study published in Nature Geoscience has found that when subduction-derived magma encounters thick continental crust, it can either penetrate the crust and produce a volcanic arc or pond beneath the surface. This is due to water diffusion within the rock which lowers its melting point by about 100 degrees Celsius. The higher viscosity of this cooled and altered magma means more time for crystals to grow inside it before they are squeezed out onto Earth’s surface during an eruption. These changes also make these volcanoes less explosive than their counterparts on thinner oceanic crust where there is no water present at all.
These subduction-derived magmas often have high levels of silica, which produces viscous lava flows like those seen in Hawaii, but when mixed with continental crusts they produce effusive eruptions that are typically low in sulfur content (like Mount St Helens). These eruptions can be very dangerous because of their low levels of sulfur emissions, which are a key factor in areas with high population densities.
The lower viscosity and explosive nature of these volcanoes can cause sudden bursts that send molten magma into the air like Mount Pinatubo’s 1991 eruption did to this village:
This part will cover how water diffusion within the rock alters its melting point by 100 degrees Celsius. The higher viscosity of this cooled and altered magma means more time for crystals to grow inside it before they are squeezed out onto Earth’s surface during an eruption. These changes produce large, relatively cool eruptions of lava that produce gentle-looking slopes.
The result? A volcano with the difference between a firecracker and an explosive device: one can be lethal while the other is just loud.
In contrast, silica-rich magma produces explosive activity as its lower viscosity allows it to rapidly rise towards the earth’s surface with less friction from the molten rock on other sides (i.e., a firecracker). This results in volcanic features like steeply sloped pyroclastic deposits and ash fallout at distances up to tens of kilometers away from the vent.
Summary: Magma that encounters thick continental crust is less explosive because more time for crystals to grow inside it before they are squeezed out onto Earth’s surface during an eruption. This results in volcanic features like steeply sloped pyroclastic deposits and ash fallout at distances up to tens of kilometers away from the vent. A volcano with different properties than a firecracker can be lethal while the other is just loud (gravelly).
The Article Title: What Happens When Magma Encounters Thick Continental Crust?
A brief description of the article is that it explains what generally happens when subduction-derived magma encounters a thick continental crust. It also contains information related to this topic. The content will be organized with a summary, followed by details including where you can find additional reading material on the subject if interested.
An explanation for why this happening and how scientists come to their conclusions was not given in the post at all, but I have found an interesting study titled “Thin vs Thick Lithosphere — Why does Earth’s Core Rotate Faster than its Surface?” which specifically tackles these questions and maybe helpful as further research into this topic.
Magma is a fluid that contains gases, suspended solid particles, crystals, and dissolved minerals. When magma encounters thick continental crust the heat energy from melting melts it quickly and causes violent eruptions to spew out lava rocks as well as gas bubbles if there was any in the molten material. The pressure of these explosive forces ruptures the overlying ground creating an opening for more magma to intrude into which makes this area an active volcano or one undergoing mountain building. This process can take centuries so we have not yet seen it happen but scientists know what will happen when they use computer simulations based on other volcanoes’ similar events.
