Taxonomy term


Stalled slabs sometimes stopped by mineral strengthening

Subduction of tectonic plates into the mantle functions as an eons-long recycling system for Earth’s crust and lithosphere. But in some subduction zones, the downgoing slabs seem to get stuck at depths of about 1,000 kilometers, held up by some unseen barrier on their journey deeper into the lower mantle. Now, scientists propose that this barrier might be related to high-pressure-induced strengthening of minerals in the rocks surrounding subducting slabs at these depths.
09 Aug 2015

Introducing Earth's inner inner core

A humongous hunk of iron — that’s how scientists have long thought of Earth’s solid inner core. But new research suggests there’s more to it than that: namely, that the inner part of the inner core may have different physical properties than the outer part. In addition to revealing a new feature in Earth’s layer-cake internal structure, the discovery may shed light on the planet’s formation, say the authors of the study, published in Nature Geoscience.
06 Jul 2015

March 29, 1936: Notes on Earth's Inner Core

On March 29, 1936, Danish seismologist Inge Lehmann wrote a letter to a colleague in which she argued that seismic waves — specifically P-waves — recorded from distant earthquakes showed some anomalous characteristics. “If you had seen so many records from these distances as I have,” she wrote, “I am sure you would not doubt that the amplitudes are abnormally small.” Within the year, Lehmann published a study based on those unusual amplitudes, work that first proposed that Earth has a solid inner core inside its liquid outer core.

29 Mar 2015

Hazard lingers after South Napa earthquake

The magnitude-6 earthquake that shook buildings and rattled wineries in California’s Napa Valley on Aug. 24, 2014, continues to affect homes in at least one neighborhood in the city of Napa more than three months later. The quake’s epicenter was about 6 kilometers south of the city, but post-quake movement, or afterslip, along the principal fault line to the north of the epicenter is ongoing, according to a fast-track report prepared by the U.S. Geological Survey (USGS) for the Federal Emergency Management Agency. Scientists involved in producing the 51-page report — released to the public on Tuesday — discussed it at a press conference at the annual meeting of the American Geophysical Union in San Francisco.

17 Dec 2014

Santiaguito Volcano's clockwork behavior provides an exceptional laboratory

If Earth breathes, Santiaguito Volcano in the Western Highlands of Guatemala could be its mouth. Roughly every half hour, like volcanic clockwork, Santiaguito’s active Caliente lava dome expands, filling with gas from depressurizing magma below. Then it exhales, often explosively, and deflates. Over the course of a day, you could almost keep time by it.

28 Sep 2014

In Turkey, the older the fault, the bigger the quake: Good news for Istanbul?

For decades, Istanbul has been bracing for a major earthquake from the dangerously active North Anatolian Fault, which passes just 20 kilometers south of Turkey’s largest city. A new study looking at the age of the fault zone may set a cap on the maximum quake size that could hit Istanbul, suggesting that the older, more mature sections of the zone in the east are capable of bigger earthquakes than the younger sections in the west, which are near the city.

05 Sep 2014

Infrasound reveals lava lake levels

The rises and falls of volcanic lava lakes are not easily tracked, especially when the lakes aren’t visible from crater rims. But recently, researchers found a way to monitor the lava lake at Chile’s Villarrica volcano using complementary methods to keep an eye on a feature they can’t always see.

22 Aug 2014

Human-induced earthquakes shake less

Occurrences of earthquakes in the Central and Eastern United States have increased since 2009 — a phenomenon that many scientists attribute to the growing use of hydraulic fracturing for fossil fuel extraction. Most agree that it’s not the fracturing itself, but the reinjection of wastewater into wells for containment beneath the surface that tends to induce seismic activity. Now, new research looking at the effects of induced seismic activity suggests that human-made earthquakes and naturally occurring tectonic earthquakes are felt differently at the surface.

21 Aug 2014

Are slow-slip earthquakes under Tokyo stressing faults?

More than 13 million people live in Tokyo, a city that has been devastated by earthquakes in the past and is likely to be rocked again. Since the massive magnitude-9 Tohoku earthquake and tsunami in March 2011, recurrence intervals for nondamaging slow-slip quakes beneath Japan's capital have shortened. And that has left seismologists to wonder if this aseismic creep could be signaling a countdown to Tokyo's next "big one."

07 Aug 2014

Books: The once and future San Andreas Fault

One of the most famous pictures of the San Andreas Fault — taken by G.K. Gilbert, the pioneering geologist whose late-19th century insights into faults and the earthquake cycle were close to prescient — shows a woman standing next to the ruptured fault immediately after the 1906 earthquake.

27 Jul 2014