What is a Volcanic Hotspot? (Educational)

Summary

Hotspots, localized high heat sources, fuel volcanic activity by generating thermal plumes that cause mantle convection. As tectonic plates move over these hotspots, magma forms at the plate's base, rises, and erupts, creating volcanoes. Over time, the weight of these volcanoes bends the plate, and as they move away from the hotspot, new volcanoes form in their place. The plate's movement can also reactivate volcanoes, even after they've drifted from the hotspot's center, due to the thermal plume's influence.

Takeaways

• 🔥 A hotspot is a localized source of high heat energy that sustains volcanism and is not a shallow magma reservoir or a direct pipe from the outer core.
• 🌋 Hotspots may originate as thermal perturbations in the boundary zone between the liquid outer core and the mantle, approximately 2900 km deep.
• 🌡️ The thermal plume from hotspots causes solid but mobile mantle to rise slowly through convection, where heated material ascends and cooler material descends.
• 🌍 Magma generation can occur at depths of up to 1500 kilometers, but individual magma blobs do not travel the entire mantle.
• 🌌 Hotspot volcanism beneath a moving tectonic plate involves the transfer of heat from pockets of melt to adjacent rock, eventually facilitating rock melting at the plate's base.
• 📈 Magma formed at the base of the tectonic plate rises through cracks and chambers, leading to volcanic eruptions on the surface.
• 🏔️ Over thousands of years, the weight of large volcanoes built on the plate causes the plate to bend downward.
• 🌿 Volcanoes that have been active over a hotspot can be rafted away on the moving plate, making way for new volcanic formations.
• 🔁 Multiple dikes can feed several volcanoes, suggesting a complex network of conduits beneath the surface.
• ⏫ The movement of the tectonic plate drags the thermal plume with it, potentially reactivating volcanic activity even after the volcano has moved off the hotspot's center.
• 📉 Erosion outpaces volcanism as eruptions decrease, and the buoyant effect of the plume diminishes, leading to the subsidence of the volcano.

Q & A

What is a hotspot in the context of volcanism?

A hotspot is a localized source of high heat energy that sustains volcanism, not a shallow magma reservoir or a direct pipe from the outer core.

Where do hotspots potentially begin and how?

Hotspots may begin as thermal perturbations in a zone between the liquid outer core and the overlying mantle about 2900 km deep, like a blowtorch.

How does convection relate to the formation of hotspots?

Convection allows solid but mobile mantle to rise slowly and convect outward due to the thermal plume from hotspots.

At what depth can magma be generated in relation to hotspots?

Magma may be generated as deep as 1500 kilometers in the mantle due to hotspot activity.

How does hotspot volcanism occur beneath a moving tectonic plate?

As the mantle melts, its heat is transferred to adjacent rock, and magma forms at the base of the plate, rising through cracks and erupting on the surface.

What happens to the volcanoes built on a moving plate over time?

Over hundreds of thousands of years, large volcanoes build on the plate, and as they move away from the hotspot, they eventually subside due to erosion and decreased buoyancy.

How does the weight of volcanoes affect the tectonic plate?

The weight of the volcanoes bends the tectonic plate downward, influencing the geological structure.

How can multiple dikes feed several volcanoes from separate conduits?

Multiple dikes can feed several volcanoes by connecting to separate conduits, allowing magma to rise and erupt in different locations.

Why can volcanoes erupt again after centuries of inactivity?

Volcanoes can erupt again after being dormant because the moving plate drags the thermal plume with it, allowing for renewed magma generation.

What is the role of erosion in the lifecycle of a volcano formed by a hotspot?

Erosion outpaces volcanism as eruptions decrease, and the buoyant effect of the plume diminishes, leading to the subsidence of the volcano.

How does the movement of the tectonic plate affect the hotspot and its volcanic activity?

The movement of the tectonic plate can cause the thermal plume to move with it, affecting the location and intensity of volcanic activity over time.