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geochronology

On the right is the first stratigraphic section of the Grand Canyon, from Powell’s 1875 report, showing what would later be termed the Great Unconformity. A is the metamorphic basement—the oldest rocks that have been contorted. B is the Precambrian Grand Canyon Supergroup, which is composed of tilted sedimentary rocks that lack fossil assemblages. C indicates flat-lying Paleozoic rocks, which contain fossils marking the explosion of life. Two unconformities can be seen at x and y, with the former marking the Great Unconformity. The image on the left is a recent photograph of the Grand Canyon from Walhalla Plateau, with the red line showing the Great Unconformity. Blue lines trace the tilted layers below the famed surface, and yellow lines trace the flat-lying sedimentary rocks on top.
Posted inNews

The Great Unconformity or Great Unconformities?

by Alka Tripathy-Lang 23 December 202231 January 2023

Some scientists think the Great Unconformity was caused by Snowball Earth’s glaciations. Recent work suggests these phenomena might not be related.

Researchers study banded iron formations in Karijini National Park, Western Australia.
Posted inNews

A Day in the Life Used to Be 17 Hours

by Emily Shepherd 10 November 202211 November 2022

The Moon was a lot closer to Earth 2.46 billion years ago, and the shorter distance contributed to shorter days.

白雪覆盖的山峰排列在青藏高原的南部边缘。
Posted inResearch Spotlights

研究揭示尼泊尔西部喜马拉雅港湾状地形的形成

Sarah Derouin, Science Writer by Sarah Derouin 19 October 202219 October 2022

研究人员通过热运动学研究发现,沿着板块汇聚界面大型逆冲断层在中下部地壳深处的地壳物质堆叠塑造了高原的生长和区域水系的发育。

A blue-gray river runs through a steep mountainous terrane, with the slopes nearest the river coated in green grasses, plants, and coniferous trees.
Posted inNews

What Can Zircons Tell Us About the Evolution of Plants?

by Alka Tripathy-Lang 5 October 202218 October 2022

The versatile mineral could contain evidence of the evolution of land plants and their effect on the sedimentary system.

A snow-capped volcano appears against a bright blue sky and is reflected in lake water of the same bright blue. In the foreground are green shrubs and a boulder.
Posted inNews

Supervolcanoes Linger a While, Then Rush to Erupt

Damond Benningfield, Science Writer by Damond Benningfield 12 September 202212 September 2022

Geologists examined crystals in rock from four massive eruptions in the Chilean Andes.

Snow-covered peaks line the southern edge of the Tibetan plateau.
Posted inResearch Spotlights

Uncovering the Formation of the Western Nepal Embayment

Sarah Derouin, Science Writer by Sarah Derouin 24 August 202219 October 2022

Using thermokinematics, researchers have found that crustal accretion along the megathrust at mid-lower crustal depths shapes plateau growth and regional drainage development.

Three field photos of the study area.
Posted inEditors' Highlights

Searching for Earth’s Oldest Rocks in its Youngest Deposits

by Peter van der Beek 18 August 202225 August 2022

By sampling and analyzing zircons from glacial eskers dating from about 20,000 years ago, the extent of the oldest known rocks on Earth can be better mapped and constrained.

Three-tiered calcite formation.
Posted inNews

Sorting Minerals Differently Could Usher a New Era for Mineralogy

by Carolyn Wilke 20 July 202214 November 2024

Grouping minerals by how they were formed yields insights into our planet’s evolution across billions of years.

Images showing the ArchKalmag14k model output for Paris (France) compared to other geomagnetic field models..
Posted inEditors' Highlights

Time-Step Filtering in Holocene Global Magnetic Field Models

by Mark J. Dekkers 9 June 20229 May 2023

Through a local fixed time-step filter, global Holocene magnetic field models remain mathematically tractable refining our insight into field variability and improving archeological dating.

Rocky high mountain landscape under a clear blue sky, with vegetation and a small lake in the foreground.
Posted inScience Updates

A Puzzle Mat for Assembling Colombia’s Geologic History

by Carolina Ortiz-Guerrero 11 April 202210 April 2023

A new database compiles all the available pieces of information about Colombia’s geochronology, offering scientists a consistent framework in which to view and study the data in a broader context.

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A view of a Washington, D.C., skyline from the Potomac River at night. The Lincoln Memorial (at left) and the Washington Monument (at right) are lit against a purple sky. Over the water of the Potomac appear the text “#AGU24 coverage from Eos.”

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Simplicity May Be the Key to Understanding Soil Moisture

23 May 202523 May 2025
Editors' Highlights

Creep Cavitation May Lead to Earthquake Nucleation

22 May 202521 May 2025
Editors' Vox

Decoding Crop Evapotranspiration

6 May 20256 May 2025
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