#tuff ring

[nocternalrandomness]

Hanahuma Bay, O'ahu, Hawaii

[earthstory]

Spattershot When the magma rising from the probable mantle plume that intersects the Mid Atlantic Ridge passed through the basaltic lump that we know as Iceland that results from this meeting and reached the surface around 2500 years before the Common Era it exploded out into the tuff ring/scoria cone in the photos. Known these days as Hverfjall, the resulting crater is around a km and a half across and is surrounded by a typical steep sided cone that is 400 metres high sitting near Lake Myvatn. Formed of layers of ash and chunks of lava that were driven out of the vent and fragmented by the pressure of expanding gases coming out of solution, it is essentially a ring of shattered debris from a lava fountain. The feature is part of a larger system known as the Krafla fissure swarm that marks an extensive weak spot in the crust that the magma forced its way through, producing a widespread set of related volcanic features from the same batch of molten rock. Loz Image credit: 1: Digital Globe 2: Orsolya and Erlend Haarberg 3:Andreas Tille https://www.icelandtravel.is/attractions/hverfjall/

[holliano]

Peachtober Day 7: Crater.

I went out to Lake Pupuke today which is a crater lake and the oldest known volcano in the Auckland Volcanic Field.

[earthstory]

Crescent

Astronaut Anton Shkaplerov captured this shot of Tortuga Island in the Galapagos from the International Space Station earlier this month. The name “Tortuga” is given to a number of islands and features such as bays around the world – it translates to “Turtle” and is given to this island because of the tortoises that lived on it. The island is obviously an old, eroding volcanic crater. It is considered a “Tuff ring”, made mostly of palagonite, an altered igneous rock formed when molten rock interacts with water and explodes. Molten rock rose up in the center of this feature, interacted with seawater, and triggered explosions that threw material outwards, forming the tuff ring.

Even though islands like this one aren’t huge and the rocks that made them up were originally broken up and fracture, they have a lot of ability to endure. I couldn't find an exact age for when this tuff ring last erupted, but it must have been hundreds of years ago. In 1844, Charles Darwin’s published writings describe this island as ”in a ruined condition, consisting of little more than half a circle open to the south”, pretty much the exact condition seen from space today.

-JBB

Image credit: https://twitter.com/Anton_Astrey/status/976851725251497986

References: https://bit.ly/2IOPes1

[wigmund]

From Earth Science Picture Of The Day; November 30, 2015:

Fort Rock Tuff Ring Photographer and Summary Author: John Kupersmith

Shown above is a volcanic feature known as a tuff ring found in south-central Oregon. It's called Fort Rock for obvious reasons. It formed an estimated 50,000-100,000 years ago when basaltic magma pushed toward the surface and contacted the mud underlying an ancient lake bottom. The resulting ring is 200-300 ft (60-90 m) high and 4,460 ft (1,360 m) in diameter -- wide enough to fit the main span of San Francisco's Golden Gate Bridge inside. For scale note the farm buildings to the right of Fort Rock. Photo taken on July 8, 2015.