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A huge tsunami in Hawaii’s past warns of future risk

Simulated tsunamis for earthquakes in several locations.
Rhett Butler

Surfers love Hawaii’s waves, and many dream of catching “the big one.” For most people living in coastal areas vulnerable to tsunamis, though, “the big one” is a bad dream. We’ve seen many devastating events over the years, but our memory is not so long that Mother Nature can’t surprise us. The 2011 tsunami in Japan testified to that.

In 2001, sediment from a past tsunami was found in a sinkhole on the southeast side of the Hawaiian island of Kaua’i. The mouth of that sinkhole is about a hundred meters from the shoreline—and over seven meters above sea level. The largest tsunami measured in the area had been three meters, courtesy of Chile’s monstrous magnitude 9.55 earthquake in 1960. Could it be that an event was big enough to send tsunami waves over seven meters high to Hawaii in the past?

Researchers Rhett Butler, David Burney, and David Walsh simulated a variety of earthquakes around the Pacific to find out. They used a model that simulates the spread of tsunami waves, creating some virtual magnitude 9.0 to 9.6 earthquakes from Alaska to Kamchatka.

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The north pole moved to the North Pole in a single human lifetime

Geology rewards an active imagination. It gives us a lot of tantalizing clues about very different times and places in Earth’s history, leaving us to try to answer “Man, what would that be like?” One of the things that's tough to image involves changing something that most of us never give a second thought—the fact that compasses point north. That’s plainly true today, but it hasn’t always been.

What we call the “north” magnetic pole—the object of your compass’ affection—doesn’t need to be located in the Arctic (it noticeably wanders there, by the way). It feels equally at home in the Antarctic. The geologic record tells us that the north and south magnetic poles frequently trade places. In fact, the signal of this magnetic flip-flopping recorded in the seafloor was the final key to the discovery of plate tectonics, as it let us see how ocean crust forms and moves over time.

That the poles flip is interesting in itself, but “Man, what would that be like?” Does the magnetic pole slowly walk along the curve of the Earth over thousands of years, meaning your compass might have pointed to some part of the equator for long stretches of time? Do the poles weaken to nothing, disappearing for a while before re-emerging in the new configuration? Do they somehow flip in the blink of an eye? Given the number of species that use the Earth’s magnetic field to navigate—especially for seasonal migrations—this is more than an academic curiosity.

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Natural underground CO2 reservoir reveals clues about storage

Reducing our emissions of carbon dioxide quickly enough to minimize the effects of climate change may require more than just phasing out the use of fossil fuels. During the phase-out, we may need to keep the CO2 we're emitting from reaching the atmosphere—a process called carbon capture and sequestration. The biggest obstacle preventing us from using CCS is the lack of economic motivation to do it. But that doesn't mean it's free from technological constraints and scientific unknowns.

One unknown relates to exactly what will happen to the CO2 we pump deep underground. As a free gas, CO2 would obviously be buoyant, fueling concerns about leakage. But CO2 dissolves into the briny water found in saline aquifers at these depths. Once the gas dissolves, the result is actually more dense than the brine, meaning it will settle downward. With time, much of that dissolved CO2 may precipitate as carbonate minerals.

But how quickly does any of this happen? Having answers will be key to understanding how well we really sequester the carbon.

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Why China’s economic growth hasn’t been getting cleaner

It’s no secret that China holds a huge amount of leverage on the future of CO2 emissions. Its incredible economic growth over the last 20 years was accompanied by a boom in greenhouse emissions. Actions to reduce that boom (as well as other pollutants) are in progress, but they haven't had any appreciable effect as of yet.

At the Copenhagen talks, China pledged a lower-carbon economy—reducing the CO2 emitted per unit of GDP (also known as “carbon intensity”) by 40-45 percent below 2005 levels by 2020. And China’s current Five Year Plan (2010-2015) set a goal of reducing carbon intensity by 17 percent while still growing GDP eight percent per year.

But between 2002 and 2009, China’s carbon intensity increased by three percent. What drove that? A new study led by Dabo Guan digs below the national level to take a look at the trends behind carbon intensity. The study suggests that, while huge progress is being made, it's still being swamped by massive growth in capacity.

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Icebergs off the Florida coast?

Grooves in the seafloor off South Carolina carved by icebergs.
Jenna C. Hill

“Snowbirds” they are called—people who escape snowy winters in the northern US by seasonally migrating to second homes in Florida. Probably about the last thing they would like to see while walking along the beach is the ice following them south. At certain times just a handful of millennia ago, it turns out, they might have been surprised to find icebergs floating by the beaches.

When Earth’s climate was colder and an ice sheet covered Canada, impressive flotillas of icebergs were occasionally launched into the Atlantic during incidents known as “Heinrich events.” Each time a batch of icebergs and glacial meltwater were vomited out, the area around the North Atlantic experienced climatic consequences. It’s thought that the infusion of freshwater gummed up the conveyor belt of Atlantic Ocean circulation, disrupting the transport of heat throughout the entire ocean basin.

Heinrich events are usually seen in ocean sediment cores as layers of gritty sediment dropped from melting icebergs onto the fine mud of the seafloor. That’s even been seen as far south as Bermuda. Closer to North America’s eastern coast, trenches carved by the undersides of large icebergs have been spotted in the mud off Nova Scotia, New Jersey, and even the Carolinas.

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Gallery: More unhealed wounds from Washington’s nearly forgotten flood

It's hard to believe the desert-like Scablands neighbors the rest of lush Washington state. Just ask J Harlen Bretz; he spent the better part of a century trying to convince his colleagues this landscape wasn't always so dry. As Ars writer Scott Johnson discovered, the Scablands are essentially wounds, still unhealed by time and erosion. These canyons were carved into the land after a series of unfathomably large floods unleashed by the catastrophic draining of great glacial lakes—half the volume of Lake Michigan splashed onto this land in less than a week.

Johnson crammed supplies into his backpack and attempted to survey the lands that Bretz obsessed over (and dedicated his life to studying). His feature outlines both the past and present experiences of exploring The Scablands, but there simply wasn't enough room for all the images he took of the breathtaking scene. So like the excess of water that led to its creation, an excess of visuals led to another Scablands birth (this time, only a gallery).

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The Scablands: A scarred landscape as strange as fiction

EASTERN WASHINGTON—Traveling from the verdant, mossy coastal belt of the Pacific Northwest, one could be forgiven for feeling that the defining characteristic of Eastern Washington is its dryness. It's a land seemingly starved of rain in the shadow of the Cascade Mountains. But the dry landscape known as the “Scablands” actually tells a story about excess—excess of water, water that was torrential and sudden.

The Scablands are essentially wounds, still unhealed by time and erosion. They cut through the land and down into the rock after a series of unfathomably large floods unleashed by the catastrophic draining of great glacial lakes—half the volume of Lake Michigan splashed onto the land in less than a week. If you can imagine that, you’ve got us beat. The story recorded in this landscape is so incredible, it took one geologist decades to convince his colleagues that he was reading it correctly.

Inflation of the modern American vernacular has devalued superlatives like “awesome” and “epic,” but we’re going to need them where we’re going.

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Fish unable to rapidly adapt to ocean acidification

A species of damselfish.

Apart from strengthening the greenhouse effect, our emissions of carbon dioxide also affect the chemistry of the oceans. When CO2 dissolves in water, it lowers the pH, which makes it more difficult for organisms to make calcium carbonate shells. The low pH also has some direct physiological effects on other marine organisms like fish. The big question mark for the future is whether these organisms can adapt or evolve to better deal with a higher-CO2 world. A new study in Nature Climate Change digs into the adaptation part of that question.

The study, led by Megan Welch at James Cook University, follows up on a previous experiment we covered in 2012. In that work, researchers put spiny damselfish hatchlings in tanks with varying levels of CO2 and tested several behaviors.

First, researchers put the fish in a split tank with one side containing the odor of a predator, and then they measured how much time the fish spent in each side. High CO2 made the animals much less likely to avoid the predator cue.

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The oceans got hotter than we thought, but the heat stayed shallow

A CTD (conductivity, temperature, depth profiler) is lowered into the water. This is the standard tool for oceanographers making measurements from a ship.
Andrew Meijers/BAS

Of the energy added to the climate system by rising concentrations of greenhouse gases, more than 90 percent has gone into the ocean. The monitoring of ocean temperatures has improved drastically over the last decade with the deployment of a vast fleet of Argo floats that drift around being our eyes and thermometers. Even so, they don’t yet cover depths greater than 2,000 meters, and their presence today doesn’t make up for their absence in decades past.

Fortunately, time travel with gadgets from the future isn’t the only way to improve our knowledge of what’s gone on in the deeps. Ocean warming also manifests itself in another way—as rising sea level. Seawater expands ever so slightly with increasing temperature. And given how absolutely massive the world ocean is, “ever so slightly” adds up. In fact, thermal expansion and melting ice have made roughly equal contributions to sea level rise so far.

Going deep

There’s been a lot of interest in recent years in quantifying the warming of the deep ocean, but not much is currently known about what's going on below 2,000 meters. In a new study published in Nature Climate Change, a group led by William Llovel at NASA’s Jet Propulsion Laboratory combines sea level rise measurements with Argo data to look for the effect of warming in the deeps.

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A maverick sandstone that calls a granite home

A Tava sandstone dike standing free of the surrounding rock, which eroded away here.
C. Siddoway

Igneous rocks are rebels. Sedimentary rocks follow straight-forward rules—they are deposited in horizontal layers, with the oldest sediments on the bottom. Igneous rocks can do what they want. Molten rock can eat away at other rocks below ground, opening up a cozy space to cool and solidify. It can also come flying—or oozing—out of a volcano, quickly crystallizing on the surface. Or it may squirt through crevices like fractures or boundaries between sedimentary layers, inserting itself as a sheet in any number of orientations. Where these walls of igneous rock cut across rock layers, they are called “dikes.”

Every now and then, when conditions are just right, sediments get to play this game, too. When they’re over-pressurized, water-soaked sands can sometimes get injected into fractures to form “clastic dikes”. Most often, these clastic dikes invade sediments or sedimentary rocks. Only very, very rarely, does sand get to turn the tables on those igneous hooligans, forming dikes of sandstone within igneous rocks.

In Colorado’s Front Range, near Colorado Springs, you can find that strange inversion. Along the Utes Pass Fault, the Tava sandstone forms dikes and similar formations within the billion-year-old Pikes Peak Granite, as well as some even older crystalline rocks to the south. Sheets of sandstone up to six meters thick cut through the rocks, which would confuse the heck out of any young geology students an instructor was mean enough to bring out there.

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