A geophysicist answers your questions about earthquakes

Today at i09, geophysicist John Bellini will be answering your earthquake-related questions, starting at 12:30 Pacific time. Read the rest

How Planet Earth got its (invisible) stripes

This image shows magnetic anomalies in the South Pacific — underwater lines where the crust of the Earth either matches up with the planet's overall magnetic polarity (reds and purples) or is completely reversed (blues). Invisible to the naked eye, these stripes run along all of Earth's ocean basins. We first noticed them in the 1950s and, at first, they were a giant mystery. Why would there be these distinct lines of magnetism, and why would the lines fluctuate in their polarity? As Chris Rowan explains at the Highly Allochthonous blog, the answer ended up being a key part of proving that chunks of the Earth's crust were moving away from each other.

Fred Vine and Drummond Matthews thought through the consequences of the hypothesis put forward by Harry Hess, that new oceanic crust was being continuously produced by the eruption of basalt at mid-ocean ridges. When combined with the facts that newly cooled basalt has a strong remanent magnetisation aligned with the ambient magnetic field, and that the Earth’s magnetic field reverses its polarity every million years or so. Vine and Matthews* argued that if seafloor spreading was indeed occurring at mid-ocean ridges, then linear positive and negative magnetic anomalies, formed from crust produced in normal and reversed polarity chrons, would form a symmetric pattern around the mid-ocean ridges, which is exactly what we see.

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Massive canyon hidden below Greenland's ice

Scientists using radio waves to estimate the thickness of the ice sheet that covers Greenland found a canyon — more than 2600 feet deep and almost 500 miles long — buried under the ice. Longer than the Grand Canyon, the Greenland canyon hasn't ever been seen by humans. It was probably last completely uncovered 4 million years ago. Read the rest

Field trip guide to Mount St. Helens

Geology blogger Dana Hunter is putting together some resources that will allow you to take yourself on a fantastic tour of America's most famous volcano. Includes maps, suggested background reading, and routes that will ensure you get to see the most interesting spots on the mountain — and learn stuff while doing it! Read the rest

Astounding backstory behind XKCD's "Time"

A week ago, Randall Munroe finished "Time", XKCD's long, running, slow-updating, 3,000+ frame comic telling the story of two people who discover an impending superflood that would destroy their society. Randall's explained in detail what was going on there, from the geology of the thing (it's set millennia in the future, amid a civilization denied the ability to jumpstart itself by the paucity of remaining fossil fuels, and the flood is modelled on a real event that sealed off the Mediterranean Sea five million years ago) to the fictional language the upland culture speaks (designed by a linguist, and still mysterious). Read the rest

Geology demonstrated with help of kitten

A slope may look stable, but that doesn't mean it will always be stable. The same geologic material can, under certain circumstances, lose its strength and integrity. Here, a geologist demonstrates how this might happen with the help of a tired kitteh. Read the rest

The Great Sahara Sea

In the 1870s, a French geographer proposed digging a canal from the Mediterranean to flood a low-lying part of the Sahara Desert. He pitched it as good for business and good for local environments, writes Ron Miller at i09. But I can't help but think of Plagues and Pleasures of the Salton Sea — a documentary about the development, culture, and slow, ongoing destruction of a salty, inland sea that accidentally formed in southern California in the first part of the 20th century. Read the rest

"Definitive proof" of Mars water

Mars' landscape was formed by flowing water, and the proof is in the pebbles. [BBC] Read the rest

Exploding things for science

Earlier this month, volcanologists blew 12 holes in an otherwise peaceful meadow in Ashford, New York. It's not that they had anything against the meadow, per se, it's just that it was a convenient place to do some real-world experiments in how explosions affect the Earth and what we can do to monitor and predict volcanic eruptions. Read the rest

Did a volcanic eruption nearly kill off ancient humans?

Short answer: We don't know. What makes this story by Erin Wayman interesting is the way it carefully breaks down an almost Hollywood-ready narrative and finds the fascinating uncertainty lurking underneath. The truth is, uncertainty is cool. Because it means there's more stuff left to discover. Read the rest

How to: Build a better sand castle

Why build a normal, weak sand castle, when you could have a defensible sand fortress?

What makes dry quicksand so deadly?

Dry quicksand was a mythical substance — normal-looking sand that could swallow you in a flash. That is, until 2004, when scientists made the stuff in a lab. (Mark told you about that development.)

In this video, geologist Matt Kuchta explains how dry quicksand is different from both wet quicksand and stable sand. Hint: Think "Jenga". Read the rest

Instant gold

Under the right conditions, veins of gold can form in just a few tenths of a second, writes Richard Lovett at Nature News. The key is the massive changes in below-ground pressure that can accompany an earthquake. Under the right conditions, water vaporizes, leaving behind crystallized minerals. Read the rest

Ancient forest off the coast of Alabama

Sixty feet under the Gulf of Mexico lie the remains of an 50,000-year-old forest. Diver and photographer Ben Raines took some amazing photos of the site and sent samples of the trees — which still look like trees — to the Lawrence Livermore National Laboratory for radiocarbon dating. You can see sap in a cross-section of the wood and, when it's cut, Raines says it still smells like fresh cypress. Read the rest

Sinkholes: Swallowing everything, including the kitchen sink

If you were horrifically fascinated (horrafinated?) by the sinkhole that swallowed Floridian Jeff Bush and his entire bedroom a week ago, you might be interested in some sinkhole science. The US Geological Survey says that sinkholes are a geologic thing. Certain areas of the country are more prone than others (which you probably knew already). But the formation of actual sinkholes in those sinkhole-prone environments can apparently be prompted by human activities, ranging from old mines that weaken the ground above them; to groundwater pumping that destabilizes the soil; to (get this) leaky faucets. The USGS does not say how many leaky faucets, or how bad a leak, it might take to trigger a sinkhole, but the basic idea is that saturating usually dry soil could cause it to shift, so you'd assume it would have to mean a lot of water leaking into the soil under the house. Read the rest

The birth of a volcano

On February 20th, 1943, Dionisio Pulido watched as a crack in his farm field collapsed in on itself and began to vomit out ash, rock, and fire. The birth of Mexico's Parícutin volcano is a story I've heard before, but I really enjoyed Dana Hunter's two-part series on the occasion of its 70th volcanaversary. Her posts really get into the perspective of Pulido and other local residents in a way I haven't seen in other accounts, and she does an amazing job of giving you a sense of just how well-documented the birth of this volcano was and why that fact matters so much. Here's Part 1 and Part 2. Read the rest

What we can learn about volcanic eruptions from the vehicles trapped in their path

The car in this photo was 13 kilometers northeast of Mount St. Helens when that volcano erupted on May 18, 1980. This photo was taken about a month later by researchers from the United States Geological Survey. At the Rosetta Stones blog, Dana Hunter has a really fascinating story — with more eerie photos — about why geologists would want to study totaled vehicles and what we can learn from machines that we can't learn from people. Read the rest

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