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Mineral Guide: Selenite

I got this selenite crystal at the first Pebble Pups meeting I attended. As a result, I researched this crystal and found lots of interesting facts, in particular, that it was very unique. This particular […]...

Synchronous diversification of Laurentian and Baltic rhynchonelliform brachiopods: Implications for regional versus global triggers of the Great Ordovician Biodiversification Event

The profound global impact of marine radiations during the Great Ordovician Biodiversification Event (GOBE) is widely appreciated; however, diversification varied among paleocontinents and these individual trajectories are less understood. Show More Summary

Fault zone characteristics and basin complexity in the southern Salton Trough, California

Ongoing oblique slip at the Pacific–North America plate boundary in the Salton Trough produced the Imperial Valley (California, USA), a seismically active area with deformation distributed across a complex network of exposed and buried faults. Show More Summary

Evidence for a reducing Archean ambient mantle and its effects on the carbon cycle

Chemical reduction-oxidation mechanisms within mantle rocks link to the terrestrial carbon cycle by influencing the depth at which magmas can form, their composition, and ultimately the chemistry of gases released into the atmosphere. Show More Summary

Formation of a future supercontinent through plate motion-driven flow coupled with mantle downwelling flow

Series of high-resolution numerical simulations of three-dimensional mantle convection were performed to examine the interaction between the drifting continental lithospheres and the underlying mantle structure for 250 m.y. from the present, and to predict the configuration of the future supercontinent. Show More Summary

Osmium isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change

Large igneous provinces (LIPs) are proposed to have caused a number of episodes of abrupt environmental change by increasing atmospheric CO 2 levels, which were subsequently alleviated by drawdown of CO 2 via enhanced continental weathering and burial of organic matter. Show More Summary

Biogenic overgrowth on detrital pyrite in ca. 3.2 Ga Archean paleosols

Regionally traceable paleosols in the lower Moodies Group of the Barberton greenstone belt (ca. 3.22 Ga, northeastern South Africa and Swaziland) contain locally abundant silicified nodules, originally composed of pedogenic carbonates and sulfates, interbedded with heavy-mineral laminae dominated by pyrite. Show More Summary

Rifting under steam--How rift magmatism triggers methane venting from sedimentary basins

During opening of a new ocean, magma intrudes into the surrounding sedimentary basins. Heat provided by the intrusions matures the host rock, creating metamorphic aureoles potentially releasing large amounts of hydrocarbons. These hydrocarbons...Show More Summary

Groundwater controls on episodic soil erosion and dust emissions in a desert ecosystem

Feedbacks between vegetation, soils, and sediment transport processes maintain arid landscapes in geomorphically active degraded states or in more biologically productive and geomorphically stable states. Landscape evolution models and...Show More Summary

Shock-metamorphosed rutile grains containing the high-pressure polymorph TiO2-II in four Neoarchean spherule layers

At least 17 spherule layers are presently known within stratigraphic units deposited between ca. 3.47 and 2.49 Ga. The spherule layers contain varying amounts of formerly molten, millimeter-sized and smaller spherules. The aggregate thickness of spherules in these layers commonly ranges from ~1 cm to as much as a few decimeters. Show More Summary

Early Triassic productivity crises delayed recovery from worlds worst mass extinction

The recovery of life after the latest Permian extinction was protracted over Early Triassic time. Detailed geochemistry of marine sections along northwest Pangea indicates that upwelling ceased at the extinction event. Nitrogen stable...Show More Summary

Persistent slip rate discrepancies in the eastern California (USA) shear zone

Understanding fault slip rates in the eastern California shear zone (ECSZ) using GPS geodesy is complicated by potentially overlapping strain signals due to many sub-parallel strike-slip faults and by inconsistencies with geologic slip rates. Show More Summary

Geological data provide support for legendary Chinese flood

Researchers have provided geological evidence for China’s “Great Flood,” a disastrous event on the Yellow River from which the Xia dynasty is thought to have been born. The flood occurred in roughly 1920 BC, they say, which is several centuries later than traditionally thought – meaning the Xia dynasty, and its renowned Emperor Yu, likely […]

Oakland building stones: Verd antique

California’s state rock is serpentine, and in this blog I’ve picked up, photographed and defended it against detractors. I’ve called serpentine beautiful, adorable, inspiring and more, but I’ve never called it a building stone. However, it can be. Serpentine in its Sunday best is called verd antique. This closeup is from the iconic I. Magnin […]

Star Trek at Fifty Years, and the First Week of a New Semester

Source: Copyright Paramount Pictures I spent part of my evening watching some Smithsonian Channel shows regarding the 50th anniversary of the initial voyage of the Starship Enterprise on Star Trek (TOS; that's "The Original Series" for those of you who aren't Trekkies). Show More Summary

Watching Foxes Along the Tuolumne River

Yes, Geotripper has been missing in action for a week or so. It's the end of summer and the start of a new semester in the academic trenches, so blogging took a back seat to other things. I should soon be back to writing and finishing the Hawai'i series, and the fall field trips will kick in pretty soon. Show More Summary

Leadfield: Scams with a Side of Geology

I've personally run into several mining or exploration scams doing field work in the west; these were small-scale attempted hoaxes perpetrated by smalltime, would-be hucksters, most of whom lacked any finesse whatsoever and all of whom...Show More Summary

Oakland building stones: Granite variations

Oakland’s buildings embody history and geology in the different types of stone that compose their facades. So how about granite? California began producing granite soon after statehood, in a stonecutting district near Sacramento where rail and barge transport was handy. At the time Oakland’s third City Hall was being designed, around 1910, many large quarries […]

Tectonic Tragedy in Italy

The 2016 Central Italy Earthquake has claimed hundreds of lives and destroyed cities. -- Read more on

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