Volcanoes and their relation to plate tectonics
Most islands are found at tectonic plate boundaries either from spreading centers On the seafloor 20 miles to the southeast of Hawaii is an active volcanic area. Plate tectonics and the Hawaiian "Hot Spot". In the early 's, the related concepts of "seafloor spreading" and "plate tectonics" emerged as powerful new . The Hawaii hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the While most volcanoes are created by geological activity at tectonic plate boundaries, the Hawaii Dana directed the first formal geological study of the hotspot's volcanics, confirming the relationship long observed by the natives.
Age was determined by the radiometric dating of radioactive isotopes of potassium and argon. Researchers estimated that the volcanoes formed during a period 81 million to 45 million years ago. Tarduno and his team determined where the volcanoes formed by analyzing the rock for the magnetic mineral magnetite. While hot lava from a volcanic eruption cools, tiny grains within the magnetite align with the Earth's magnetic fieldand lock in place once the rock solidifies.
Researchers were able to verify the latitudes at which the volcanoes formed by measuring the grains' orientation within the magnetite. Paleomagnetists concluded that the Hawaiian hotspot had drifted southward sometime in its history, and that, 47 million years ago, the hotspot's southward motion greatly slowed, perhaps even stopping entirely. Pele deityHalemaumau Craterand Hawaiian mythology The possibility that the Hawaiian islands became older as one moved to the northwest was suspected by ancient Hawaiians long before Europeans arrived.
Pele was born to the female spirit Haumeaor Hinawho, like all Hawaiian gods and goddesses, descended from the supreme beings, Papa, or Earth Motherand Wakeaor Sky Father. Pele fled southeast to the island of Oahu. Pele's mythical flight, which alludes to an eternal struggle between volcanic islands and ocean waves, is consistent with geologic evidence about the ages of the islands decreasing to the southeast.
Three of the earliest recorded observers of the volcanoes were the Scottish scientists Archibald Menzies in James Macrae in and David Douglas in Just reaching the summits proved daunting: The United States Exploring Expedition spent several months studying the islands in — Dana stayed with missionary Titus Coanwho would provide decades of first-hand observations. He confirmed that the islands' age increased with their distance from the southeastern-most island by observing differences in their degree of erosion.Hot spot formation
He also suggested that many other island chains in the Pacific showed a similar general increase in age from southeast to northwest. Dana concluded that the Hawaiian chain consisted of two volcanic strands, located along distinct but parallel curving pathways. He coined the terms "Loa" and "Kea" for the two prominent trends. Dana proposed that the alignment of the Hawaiian Islands reflected localized volcanic activity along a major fissure zone. Dana's "great fissure" theory served as the working hypothesis for subsequent studies until the midth century.
Dutton 's expedition, who refined and expanded Dana's ideas. Most notably, Dutton established that the island of Hawaii actually harbored five volcanoes, whereas Dana counted three. Stimulated by Dutton's expedition, Dana returned inand published many accounts of his expedition in the American Journal of Science.
In he published the most detailed manuscript of its day, and remained the definitive guide to Hawaiian volcanism for decades. The next century was a period of thorough investigation, marked by contributions from many top scientists. Since that time, advances have enabled the study of previously limited areas of observation e.
These low seismic velocity zones often indicate hotter and more buoyant mantle material, consistent with a plume originating in the lower mantle and a pond of plume material in the upper mantle. The magma's original temperature was found in two ways, by testing garnet 's melting point in lava and by adjusting the lava for olivine deterioration.
However, it has been shown that other plumes display highly variable surface heat fluxes and that this variability may be due to variable hydrothermal fluid flow in the Earth's crust above the hotspots. This fluid flow advectively removes heat from the crust, and the measured conductive heat flow is therefore lower than the true total surface heat flux.
Movement[ edit ] Hawaiian volcanoes drift northwest from the hotspot at a rate of about 5—10 centimeters 2.
Prior to the bend, the hotspot migrated an estimated 7 centimeters 2. The  expedition drilled six seamounts and tested the samples to determine their original latitude, and thus the characteristics and speed of the hotspot's drift pattern in total. The large difference between the youngest and oldest lavas between Emperor and Hawaiian volcanoes indicates that the hotspot's velocity is increasing.
For example, Kohala, the oldest volcano on Hawaii island, is one million years old and last eruptedyears ago, a period of just underyears; whereas one of the oldest, Detroit Seamount, experienced 18 million or more years of volcanic activity.
Hotspot Volcanoes: Earthquake Risk in Hawaii
It is unknown whether the seamount chain has been subducting under the Eurasian Plate, and whether the hotspot is older than Meiji Seamount, as any older seamounts have since been destroyed by the plate margin. It is also possible that a collision near the Aleutian Trench had changed the velocity of the Pacific Plate, explaining the hotspot chain's bend; the relationship between these features is still being investigated.
Pu'u 'O'o is one of the most active volcanoes in the world, and has been continuously erupting since January 3, The composition of the volcanoes' magma has changed significantly according to analysis of the strontium — niobium — palladium elemental ratios.
The Emperor Seamounts were active for at least 46 million years, with the oldest lava dated to the Cretaceous Periodfollowed by another 39 million years of activity along the Hawaiian segment of the chain, totaling 85 million years. Data demonstrate vertical variability in the amount of strontium present in both the alkalic early stages and tholeitic later stages lavas. Some of these volcanoes build up to the surface of the ocean and become islands.
Over millions of years the plate may move across the 'hot spot' and the original volcano become extinct but a new volcano will begin to form in the area of the 'hot spot. This movement has left the northwest trending island chain of over 20 islands and atolls we call Hawaii. As islands move northwest, away from the 'hot spot,' they begin to erode and become volcanically inactive.
Over time the island may erode so much it is no longer an island but an underwater seamount. Kauai is the oldest of the main Hawaiian Islands now, having formed some 5 million years ago, with its volcano considered to be extinct and fully in the process of erosion. Oahu is next, its volcanism is considered to be inactive. Then Maui with its Haleakala crater that could still come to life one more time. And the youngest island is the 'Big Island' of Hawaii itself, with surface lavas all less than one million years old.
Hawaii hotspot - Wikipedia
It still has active volcanism. On the seafloor 20 miles to the southeast of Hawaii is an active volcanic area with periodic eruptions. This area is called Loihi and will be the site of the next Hawaiian Island if geologic processes continue as they have for millions of years but it may be over 10, years before this happens. Pele, goddess of fire, as portrayed in a mural at the Jagger Museum on the rim of Kilauea.
Map of the five volcanos that made the big island of Hawaii left. Steam vents Volcano House is in the background where tourists eat and stay and sulfur deposits near the rim of Kilauea volcano right. GA images Kilauea volcano is active on its flanks today. Inside the volcano is Halema'uma'u, a pit crater inside the larger Kilauea crater, in the background of this image taken in when Halema'uma'u was not active.
GA image Sulfur Banks is an area near the visitor center at the rim of Kilauea volcano left. Closeup of the sulfur deposits reveal beautiful crystals right. GA images Hawaii has active volcanism today. Kohala last erupted 60, years ago and Mauna Kea last erupted 3, years ago.
These two volcanoes are considered dormant. Hualalai's last eruption was in Only two of Hawaii's volcanoes are active today - Mauna Loa and Kiluaea. Mauna Loa erupted in and Kilauea is considered to be one of the most active volcanoes on Earth today. It has erupted over 30 times in the last 40 years. Hawaii is one of the few places on Earth where you can safely watch the volcanic processes that shape our Earth. Cross sectional diagram of Kilauea volcano from the Jagger Museum showing the east rift zone most active area today.
GA image Halema'uma'u, a pit crater, inside Kilauea Caldera started erupting in creating an almost constant plume of steam and volcanic gases including sulphur dioxide. In fact, if you were at the National Park, prior to Mayafter dark then Halema'uma'u crater was usually glowing red from a lava lake in the bottom of Halema'uma'u - best viewing was from the Jagger Museum.
All this changed in May At night, prior to the eruption, the lava lake in the bottom of Halema'uma'u reflected off the stream of volcanic gases right.
GA images Kilauea volcano has active vents that erupt in various places on the southeastern side of Hawaii. The 'hot spot' volcanos are considered to be gentle volcanos and different than the violent volcanic eruption from Mount Saint Helens that killed many people in the State of Washington in Pu'u O'o vent August GA images Erupting vents inside Pu'u O'o vent.
GA image Pu'u O'o vent became active in and was the primary source of surface lava until May in the east rift zone of Kilauea. It is about 10 miles east of Kilauea crater and far from most roads but helicopters could safely take you there for an aerial view.
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These flows were sometimes on the surface where they covered subdivisions and sometimes in lava tubes that reached the ocean. Helicopter view of lava flowing toward the ocean left.
GA images Lava flow toward the ocean with steam left. Crack in recent lava flow shows cooled surface but still molten layers under it right. GA images Warning sign near a recent surface lava flow reminds visitors that volcanism can be dangerous left. Trail to recent lava flows in the National Park are sometimes marked with yellow tags to help visitors see the lava flows and remain safe right. GA images Lava flowing into the ocean is not a common sight but, in Hawaii, it can be possible for the general tourist to view this.
Hawaii's lava is slow moving and somewhat predictable in its path. The Hawaii Volcanoes National Park sets up a marked trail and signs to guide tourists for the best views of the eruptions of Kiluaea while keeping them reasonably safe. Every day the situation with the location and activity level of the lava changes and park personnel are kept busy during active periods. Lava Flows GA images Lava flows from Pu'u O'o during the summer of above provided great viewing for anyone who was willing to walk about a mile along the marked path.
The flows were active but at the speed of a slowly moving snail so viewing them was easy. Flowing lava may be over 2, degrees Fahrenheit with the air next to it close to degrees. It is easy not to get too close to the flowing lava as you break out into a sweat when you are a few feet away. Usually the Trade Winds are blowing near the flowing lava which allows rather close safe inspection as the winds help to cool onlookers down a bit.
Notice how the molten red lava that is flowing cools on the surface. This flow is distinctly pahoehoe ropey and it is easy to see how it forms. GA image Hawaii's volcanic eruptions are known for their gentleness and resulting shield volcanoes. Fountains and fissures do break out occassionally in the Hawaiian volcanos but these are not the norm.
Hotspot Volcanoes: Earthquake Risk in Hawaii
GA image Steam from new lava flow escapes - note yellow markers in background that mark a safe trail for tourists to view the recent lava flows. GA image Magma turns to lava as molten rock comes to the surface. Molten rock is considered magma when it is under Earth's crust, but when extruded from the crust as in a volcanic eruption it is called lava.
The lava flows through cracks, vents and fissures, adding to Hawaii's land mass. Lava cliff from a recent lava flow. GA image Fingers of pahoehoe lava seem to drip down the lava cliff left.
Pahoehoe flow over older, eroded, lava flow right. GA images Pahoehoe lava hardens into interesting textures.
- Hawaii: Geology, Plate Tectonics/Hot Spot
- Hawaii hotspot
- Plate Tectonics and the Hawaiian Hot Spot
GA images Closeup of glassy surface of new pahoehoe lava. GA image Pahoehoe lava has a ropey texture. Pahoehoe and aa lava flows above. GA image Aa lava has a rough and clinkery texture. Aa lava flow left. Closeup of aa lava right. GA images Dragon's teeth, Maui. GA image Dragon's teeth in Maui is a unique lava flow that was influenced by high waves as the ancient lava flow hit the ocean. The wave energy at the time of the flowing lava was strong enough to curl up the edges of the lava before it cooled leaving these unique giant tooth-like structures.
Visitors enter through a 'skylight' collapsed roof of a lava tubewalk a ways through the tube and exit via another 'skylight. GA images Lava tubes develop as the lava flows and hardens on the outside. The inside continues to flow and may drain out of the 'lava tube' entirely. Some of these lava tubes are small but some are very large as much as 20 feet in diameter.
Many of the lava tubes have a flat bottom as the lava hardened when it slowed down and remind some people of subway tunnels.
When the top of a lava tube breaks through it is called a 'skylight. GA images Tree molds form as lava flows around living trees. If the lava flow stays deep around the tree it will leave a below grade hole as the tree burns and dies. If the lava flow moves on through it will often leave standing tree molds that are hollow as the tree burns and dies but standing above grade because the flow went on past.