Extraterrestrial Hot SpotsOne of the most geologically active places in the solar system is the hot spots that may be cracking up the icy surface of Jupiter’s moon Europa. Many astrophysicists think that warm ice is rising up through the colder ice of the outer crust, causing it to crack with lenticulae, or “freckles,” on the moon’s surface.Hot Spots are CoolIsland volcanoes that form over hot spots are generally less explosive than volcanic arcs that form over subduction zones.
It's Like Watching Grass Grow (or Plates Move)...
The Pacific plate moves about as quickly as your fingernails grow: roughly 10 centimeters (4 inches) per year.A hot spot is a region deep within the Earth’s mantle from which heat rises through the process of convection. This heat facilitates the melting of rock at the base of the lithosphere, where the brittle, upper portion of the mantle meets the Earth’s crust. The melted rock, known as magma, often pushes through cracks in the crust to form volcanoes.Hot spot volcanism is unique because it does not occur at the boundaries of Earth’s tectonic plates, where all other volcanism occurs. Instead it occurs at abnormally hot centers known as mantle plumes. Scientific models depict these plumes of molten rock almost like a lava lamp, with a rising bulbous head fed by a long, narrow tail that originates in the mantle. As the plume head reaches the lithosphere, it spreads into a mushroom shape that reaches roughly 500 to 1000 kilometers (310 to 621 miles) in diameter. These features are called diapirs.Scientists have different theories about where hot spots form. The dominant theory, framed by Canadian geophysicist J. Tuzo Wilson in 1963, states that hot spot volcanoes are created by exceptionally hot areas fixed deep below the Earth’s mantle. More recent scientific studies suggest that these hot spots may be found at more shallow depths in the Earth’s mantle and may migrate slowly over geologic time rather than stay fixed in the same spot.A volcano above a hot spot does not erupt forever. Attached to the tectonic plate below, the volcano moves and is eventually cut off from the hot spot. Without any source of heat, the volcano becomes extinct and cools. This cooling causes the rock of the volcano and the tectonic plate to become more dense. Over time, the dense rock sinks and erodes. A new and active volcano develops over the hot spot, creating a continuous cycle of volcanism.Hot Spot FeaturesMost scientists think that 40 to 50 hot spots exist around the world, although this number varies widely because of differing definitions of what a hot spot is. Major hot spots include the Iceland hot spot, under the island of Iceland in the North Atlantic; the Réunion hot spot, under the island of Réunion in the Indian Ocean; and the Afar hot spot, located under northeastern Ethiopia.Volcanic activity at hot spots can create submarine mountains known as seamounts. Some scientists estimate that seamounts make up 28.8 million square kilometers (17.9 million square miles) of the Earth’s surface, an area larger than any other habitat. Depending on the amount of volcanic activity, seamounts can rise hundreds or thousands of meters from the seafloor.The Louisville Seamount Chain, for example, is comprised of over 80 seamounts that extend in a 4,000 kilometer (2,485 mile) arc in the South Pacific Ocean, about 1,500 kilometers (932 miles) from Wellington, New Zealand. The seamounts originated from a single hot spot and have been slowly transported in a northwest direction by the Pacific plate.Hot spot seamounts that reach the surface of the water can create entire chains of islands, such as the U.S. state of Hawaii. Scientists think that this volcanic chain of islands has been forming for at least 70 million years over a hot spot underneath the Pacific plate. The Hawaiian Islands were created one right after the other as the plate moved northwest—almost like an island factory. Of all the inhabited Hawaiian Islands, Kauai is located farthest from the presumed hot spot and has the most eroded and oldest volcanic rocks, dated to be around 5.5 million years old. Meanwhile, on the “Big Island” of Hawaii, the oldest rocks are less than 0.7 million years old and volcanic activity continues to create new land.Hot spots can also develop beneath continents. The Yellowstone hot spot, for example, has produced a series of volcanic features that extend in a northeastern direction. The features stretch from the U.S. states of Idaho and Oregon, some 650 kilometers (400 miles) to northwest Wyoming. Over 16.5 million years, the hot spot has generated 15 to 20 massive eruptions that left large volcanic depressions called calderas. The McDermitt Volcanic Field, located on the Nevada-Oregon border, is the hot spot’s oldest large feature. It formed from an eruption roughly 16.1 million years ago. The active Yellowstone Caldera, in Yellowstone National Park in northwest Wyoming, is the hot spot’s youngest large feature, having last erupted just 640,000 years ago.Hot spots don't always create volcanoes that spew rivers of lava. Sometimes, the magma heats up groundwater under the Earth’s surface, which causes water and steam to erupt like a volcano. These eruptions are called geysers. A famous geyser is Old Faithful in Yellowstone National Park. When it erupts, the water is 95.6 degrees Celsius (204 degrees Fahrenheit) and can reach more than 55 meters (180 feet) high.
Term Part of Speech Definition Encyclopedic Entry abnormal Adjective
active volcano Noun
volcano that has had a recorded eruption since the last glacial period, about 10,000 years ago.
part of the outline of a circle.
fragile or easily broken.
swollen or shaped like a bulb.
large depression resulting from the collapse of the center of a volcano.
Encyclopedic Entry: caldera continent Noun
one of the seven main land masses on Earth.
Encyclopedic Entry: continent continuous Adjective
transfer of heat by the movement of the heated parts of a liquid or gas.
rocky outermost layer of Earth or other planet.
Encyclopedic Entry: crust dense Adjective
having parts or molecules that are packed closely together.
to illustrate or show.
indentation or dip in the landscape.
width of a circle.
dome-shaped geologic feature (intrusion) where more fluid material is forced into brittle overlying rock.
main or most important.
our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.
Encyclopedic Entry: Earth erode Verb
to wear away.
to explode or suddenly eject material.
to guess based on knowledge of the situation or object.
to enlarge or continue.
no longer existing.
to help or make easier.
to create or begin.
having to do with the physical formations of the Earth.
person who studies the material and activity of the Earth and its atmosphere.
natural hot spring that sometimes erupts with water or steam.
Encyclopedic Entry: geyser groundwater Noun
water found in an aquifer.
Encyclopedic Entry: groundwater habitat Noun
environment where an organism lives throughout the year or for shorter periods of time.
Encyclopedic Entry: habitat hot spot Noun
intensely hot region deep within the Earth that rises to just underneath the surface. Some hot spots produce volcanoes.
Encyclopedic Entry: hot spot inhabit Verb
to live in a specific place.
body of land surrounded by water.
Encyclopedic Entry: island lava Noun
molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.
outer, solid portion of the Earth. Also called the geosphere.
Encyclopedic Entry: lithosphere magma Noun
molten, or partially melted, rock beneath the Earth's surface.
Encyclopedic Entry: magma mantle Noun
middle layer of the Earth, made of mostly solid rock.
Encyclopedic Entry: mantle mantle plume Noun
geologic feature where rock (magma) rises through Earth's mantle to become a molten intrusion in Earth's crust.
very large or heavy.
to move from one place or activity to another.
solid material turned to liquid by heat.
to begin or start.
part of a whole.
to assume in the absence of facts to the contrary.
any area on the Earth with one or more common characteristics. Regions are the basic units of geography.
Encyclopedic Entry: region rock Noun
natural substance composed of solid mineral matter.
to eject or discharge violently.
tectonic plate Noun
large, moveable segment of the Earth's crust.
to move material from one place to another.
one of a kind.
an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.
Encyclopedic Entry: volcano