what are hot spots caused by answers
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what is a hot spot?
A hot spot is an area on Earth over a mantle plume or an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma. The magma plume causes melting and thinning of the rocky crust and widespread volcanic activity.
n 1963, J. Tuzo Wilson, the Canadian geophysicist who discovered transform faults,
came up with an ingenious idea that became known as the “hotspot” theory. Wilson noted that in certain locations around the world, such as Hawaii, volcanism has been active for very long periods of time.
This could only happen, he reasoned, if relatively small, long-lasting,
and exceptionally hot regions — called hotspots — existed below the plates that would provide localized sources of high heat energy (thermal plumes) to sustain volcanism. Specifically, Wilson hypothesized that the distinctive linear shape of the Hawaiian Island-Emperor Seamounts chain resulted from the Pacific Plate moving over a deep,
stationary hotspot in the mantle, located beneath the present-day position of the Island of Hawaii.
Heat from this hotspot produced a persistent source of magma by partly melting the overriding Pacific Plate.
The magma, which is lighter than the surrounding solid rock
The magma, which is lighter than the surrounding solid rock, then rises through the mantle and crust to erupt onto the seafloor,
forming an active seamount.
Over time, countless eruptions cause the seamount to grow until it finally emerges above sea level to form an island volcano. Wilson suggested that continuing plate movement eventually carries the island beyond the hotspot, cutting it off from the magma source, and volcanism ceases. As one island volcano becomes extinct,
another develops over the hotspot, and the cycle is repeated.
This process of volcano growth and death, over many millions of years,
has left a long trail of volcanic islands and seamounts across the Pacific Ocean floor.
According to Wilson’s hotspot theory,
the volcanoes of the Hawaiian chain should get progressively older and become more eroded the farther they travel beyond the hotspot. The oldest volcanic rocks on Kauai, the northwesternmost inhabited Hawaiian island,
are about 5.5 million years old and are deeply eroded. By comparison, on the “Big Island” of Hawaii — southeasternmost in the chain and presumably still positioned over the hotspot — the oldest exposed rocks are less than 0.7 million years old and new volcanic rock is continually being formed.
Hawaiian Islands
the possibility that the Hawaiian Islands become younger to the southeast was suspected by the ancient Hawaiians,
long before any scientific studies were done. During their voyages, sea-faring Hawaiians noticed the differences in erosion, soil formation, and vegetation and recognized that the islands to the northwest (Niihau and Kauai) were older than those to the southeast (Maui and Hawaii). This idea was handed down from generation to generation in the legends of Pele,
the fiery Goddess of Volcanoes. Pele originally lived on Kauai.
When her older sister Namakaokahai, the Goddess of the Sea, attacked her, Pele fled to the Island of Oahu. When she was forced by Namakaokahai to flee again,
Pele moved southeast to Maui and finally to Hawaii, where she now lives in the Halemaumau Crater at the summit of Kilauea Volcano. The mythical flight of Pele from Kauai to Hawaii,
which alludes to the eternal struggle between the growth of volcanic islands from eruptions and their later erosion by ocean waves, is consistent with geologic evidence obtained centuries later that clearly shows the islands becoming younger from northwest to southeast.
Hawaii is perhaps the best known hotspot
Although Hawaii is perhaps the best known hotspot, others are thought to exist beneath the oceans and continents. More than a hundred hotspots beneath the Earth’s crust have been active during the past 10 million years. Most of these are located under plate interiors (for example, the African Plate),
but some occur near diverging plate boundaries. Some are concentrated near the mid-oceanic ridge system, such as beneath Iceland, the Azores, and the Galapagos Islands.
A few hotspots are thought to exist below the North American Plate.
Perhaps the best known is the hotspot presumed to exist under the continental crust in the region of Yellowstone National Park in northwestern Wyoming.
Here are several calderas (large craters formed by the ground collapse accompanying explosive volcanism) that were produced by three gigantic eruptions during the past two million years, the most recent of which occurred about 600,000 years ago. Ash deposits from these powerful eruptions have been mapped as far away as Iowa, Missouri, Texas, and even northern Mexico.
The thermal energy of the presumed Yellowstone hotspot fuels more than 10,000 hot pools and springs, geysers (like Old Faithful), and bubbling mudpots (pools of boiling mud).
A large body of magma, capped by a hydrothermal system (a zone of pressurized steam and hot water), still exists beneath the caldera.
Recent surveys demonstrate that parts of the Yellowstone region rise and fall by as much as 1 cm each year, indicating the area is still geologically restless. However, these measurable ground movements, which most likely reflect hydrothermal pressure changes, do not necessarily signal renewed volcanic activity in the area.
Have you ever wondered
Have you ever wondered just how many different species of living things there are on our planet?
This is a hard question to answer! The actual number of living organisms on Earth is unknown to us,
but so far, scientists have described up to 1.7 million species of living organisms. Of those, over 1.3 million are animals, 100,000 are fungi, over 300,000 are plants, plus countless species of bacteria, algae, and viruses .
This incredible variety of life forms is what we know as biodiversity,
that is, all kinds of life existing in a certain place.
It is difficult to know the actual number of living organisms on Earth,
or what percentage of these organisms are already known to us.
In some cases, there is quite a lot of debate.
For example, the estimated number of animals varies from 2 to 11 million species.
And while the average estimate of known plant species is somewhere around 300,000, the predicted number of plants,
including yet unknown species, is around 450,000 species . In any case, scientists agree that,
despite the great number of species that have already been discovered, it is likely that there is an even larger number of species yet to be discovered.
Now you might wonder, “Okay, that is nice to know, but what difference does it make?”
It makes all the difference! When we are trying to protect the biodiversity on our planet,
knowing how many species are out there is as important as knowing how and where they are distributed around the globe, so that we can decide which areas of the planet are priorities for conservation, especially if we cannot protect every area.
Most volcanoes
Most volcanoes happen at junctures where great slabs of the Earth’s rocky surface—called tectonic plates—slide under,
over or past each other. But the Earth also sports dozens of anomalous “hotspots”—volcanic regions that scientists can’t explain simply using plate tectonics. Hotspots can happen in the middle of oceanic plates—Hawaii is a case in point.
Or they can occur amid continental plates—Yellowstone, for example, smokes and spews far from the grinding edges of tectonic plates. Other hotspots, such as Iceland, display volcanism greatly exceeding what geologists would expect at a mid-ocean ridge where plates are moving apart from one another.
What is magma ?
Magma is the molten or semi-molten natural material from which all igneous rocks are formed.
Magma is found beneath the surface of the Earth,
and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites.
Besides molten rock, magma may also contain suspended crystals and gas bubbles.
Magma is produced by
Magma is produced by melting of the mantle or the crust in various tectonic settings, which on Earth include subduction zones, continental rift zones, mid-ocean ridges and hotspots. Mantle and crustal melts migrate upwards through the crust where they are thought to be stored in magma chambers[6] or trans-crustal crystal-rich mush zones.
During magma’s storage in the crust, its composition may be modified by fractional crystallization,
contamination with crustal melts, magma mixing, and degassing. Following its ascent through the crust,
magma may feed a volcano and be extruded as lava,
or it may solidify underground to form an intrusion,
such as a dike, a sill, a laccolith, a pluton, or a batholith.
While the study of magma has relied on observing magma after its transition into a lava flow,
magma has been encountered in situ three times during geothermal drilling projects, twice in Iceland (see Use in energy production) and once in Hawaii.
Do most volcanoes happen underwater?
More than 70 percent of all volcanic eruptions occur underwater and scientists are in the dark when it comes to understanding underwater volcanoes because the eruptions are cloaked from view by thousands of feet of water.
