Category Archives: Geology

The unique geology of Macquarie Island

macquarie island

Macquarie Island is located in the south-west Pacific Ocean, between Australia and New Zealand, and officially belongs to the Australian state of Tasmania. The island is tiny, only 5 km (3.1 mi) wide and 35 km (21.7 mi) long, covering a total area of 128 km2 (49 sq mi). It is a unique place: it is the only sub-Antarctic island to be fully oceanic in origin, and it is the only known site on Earth where an ophiolite complex is … Continue reading

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New, tighter timeline confirms ancient volcanism aligned with dinosaurs’ extinction

A definitive geological timeline shows that a series of massive volcanic explosions 66 million years ago spewed enormous amounts of climate-altering gases into the atmosphere immediately before and during the extinction event that claimed Earth’s non-avian dinosaurs, according to new research from Princeton University. A primeval volcanic range in western India known as the Deccan Traps, which were once three times larger than France, began its main phase of eruptions roughly 250,000 years before the Cretaceous-Paleogene, or K-Pg, extinction event, … Continue reading

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The Holocene

Paleogeographic reconstruction of the North Sea approximately 9,000 years ago during the early Holocene and after the end of the last ice age.

Further to my post recently on geological periods, I thought you might be interested in the period we are in now – The Holocene. It turns out that this also breaks down into smaller time scales known as chronozones and we are are now in the Subatlantic chronozone. – Who knew? – Deskarati This video is called Holocene by Bon Iver The Holocene is a geological epoch which began at the end of the Pleistocene (at 11,700 calendar years BP) … Continue reading

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Geological Periods

geological periods 2

A geologic period is one of many sub-divisions of geologic time enabling the cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions into which geologists have split the earth’s history. Eons and eras are larger subdivisions than periods while periods themselves may be divided into epochs and ages.

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One of the fundamental principles of geology is that sedimentary rocks are deposited in horizontal layers due to gravity. There are some exceptions, including cross beds and rocks deposited on steep slopes, but the rule is a very good guide. If sedimentary rocks are deposited in horizontal layers that are parallel to Earth’s surface, then what you’re seeing here requires something else. The vertical pattern is dominated by erosion along fractures. Fractures called joints often appear in parallel sets; water … Continue reading

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The story of pahoehoe

This is really a fascinating photo. Did you ever think that a chain link fence would hold up against lava? Of course, given enough time, the fence isn’t going to hold up, but this photo illustrates some of the most interesting behaviors of pahoehoe lava flows like those that are migrating through Pahoa on the big island of Hawaii right now. Most people are familiar with pahoehoe lava based on the wrinkled surface textures, like those in the foreground of … Continue reading

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Supervolcano blast would blanket U.S. in ash

A new simulation illustrates the explosiveness of the volcano that lurks beneath Yellowstone National Park in Wyoming. Around 640,000 years ago, the volcano blew its top and coated North America with roughly 1,000 cubic kilometers of ash, enough to fill Lake Erie twice over. A simulation of the eruption described August 27 in Geochemistry, Geophysics, Geosystems reveals that a similar outburst today would bury Billings, Mont., in more than a meter (about 40 inches) of volcanic glass shards and pulverized … Continue reading

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Where does desert sand come from?

Sand is a great traveller. Go to the seaside for the day and it’ll ride home on your shoes or sneak into your picnic sandwiches. You may wonder, as you shake sand from your bag on the beach: ‘where did all this sand come from and how long’s it been here?’ Dr Pieter Vermeesch and colleagues had the same question about the sand in the Namib Sand Sea – one of the world’s oldest and largest sand deserts. We know little … Continue reading

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How The Sahara Desert Was Made

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Volcano Eruption in Papua New Guinea

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Mystery solved: ‘Sailing stones’ of Death Valley seen in action for the first time

moving stones

Racetrack Playa is home to an enduring Death Valley mystery. Littered across the surface of this dry lake, also called a “playa,” are hundreds of rocks — some weighing as much as 320 kilograms (700 pounds) — that seem to have been dragged across the ground, leaving synchronized trails that can stretch for hundreds of meters. What powerful force could be moving them? Researchers have investigated this question since the 1940s, but no one has seen the process in action … Continue reading

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Aogoshima Island

This is an aerial view of Aogoshima Island, one of about a dozen volcanic islands south of Tokyo in the Philippine Sea, seven of which are inhabited. Aogoshima is the southernmost of these inhabited islands. In the Western Pacific, the Pacific Plate is subducting beneath a series of plates, including the Eurasian plate to the North beneath Japan and the Philippine Sea plate here. That subduction leads to a linear series of volcanoes trending south from Tokyo where the Pacific, … Continue reading

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Devils Tower


Devils Tower is anigneous intrusion or laccolith in the Black Hills near Hulett and Sundance in Crook County, northeastern Wyoming, above the Belle Fourche River. It rises dramatically 1,267 feet (386 m) above the surrounding terrain and the summit is 5,114 feet (1,559 m) above sea level. Devils Tower was the first declared United States National Monument, established on September 24, 1906, by President Theodore Roosevelt. The Monument’s boundary encloses an area of 1,347 acres (545 ha). In recent years, about 1% of the Monument’s 400,000 annual visitors climbed Devils Tower, mostly using traditional climbing techniques. The Arapaho, Crow, Cheyenne, Kiowa, Lakota, and Shoshone tribes had cultural … Continue reading

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Normal Fault


This image shows a classic normal fault in fairly young (<20 million year old) sedimentary rocks outside of Harrison, Montana. The fault plane is clear and it dips to the right in this image. If you look at both sides of the fault, layers on the right and left are nearly identical, just the layers on the right have moved down. The layers even have specific features; the more resistant layer sticks out, while the weaker layer has been used … Continue reading

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Volcanic rocks are born as lavas or layers of ash, and stack up eruption after eruption, sometimes thick enough to form islands such as Japan and Iceland (in the featured image) on the mid Atlantic ridge. Much of the rock in the latter is basaltic, but gets transformed after its birth into a variety of chewed up and brightly coloured rock remnants. As ground or sea water percolates into the lava, it interacts with the magma or pressure heated rocks … Continue reading

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Viruses Make Zombies of Deep Sea Vent Bacteria


Viruses hijack bacteria that feed on sulfur-spewing vents on the ocean’s floor and then reprogram the bacteria’s DNA, a new study finds, essentially brainwashing the bacteria to devour more of the chemicals erupting from the vents. The bacteria then burn up their stored sulfur reserves faster. These overeating zombie bacteria create excess energy that the viruses use to reproduce, until the bacteria burst and release a fresh wave of virus particles. Microbiologists knew that surface-dwelling viruses could take over bacteria that … Continue reading

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Unique Mineral Discovered In Australia

Screen Shot

A previously unknown mineral has been discovered in a remote location in Western Australia. The mineral, named putnisite, appears purple and translucent, and contains strontium, calcium, chromium, sulphur, carbon, oxygen and hydrogen, a very unusual combination. While dozens of new minerals are discovered each year, it is rare to find one that is unrelated to already-known substances. “Most minerals belong to a family or small group of related minerals, or if they aren’t related to other minerals they often are to a … Continue reading

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Moeraki Boulders


The Moeraki Boulders are unusually large and spherical boulders lying along a stretch of Koekohe Beach on the wave-cut Otago coast of New Zealand between Moeraki and Hampden. They occur scattered either as isolated or clusters of boulders within a stretch of beach where they have been protected in a scientific reserve. The erosion by wave action of mudstone, comprising local bedrock and landslides, frequently exposes embedded isolated boulders. These boulders are grey-colored septarian concretions, which have been exhumed from … Continue reading

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Scientists reconstruct ancient impact that dwarfs dinosaur extinction blast


Piture this: A massive asteroid almost as wide as Rhode Island and about three to five times larger than the rock thought to have wiped out the dinosaurs slams into Earth. The collision punches a crater into the planet’s crust that’s nearly 500 kilometers (about 300 miles) across: greater than the distance from Washington, D.C. to New York City, and up to two and a half times larger in diameter than the hole formed by the dinosaur-killing asteroid. Seismic waves … Continue reading

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How Earth might have looked

Break-up of the supercontinent Gondwana about 130 Million years ago could have lead to a completely different shape of the African and South American continent with an ocean south of today’s Sahara desert, as geoscientists from the University of Sydney and the GFZ German Research Centre for Geosciences have shown through the use of sophisticated plate tectonic and three-dimensional numerical modelling. The study highlights the importance of rift orientation relative to extension direction as key factor deciding whether an ocean … Continue reading

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