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Monsoonal upwelling in the western Arabian Sea since the middle Miocene

The Asian monsoon has long been argued to be a product of the Himalaya–Tibetan Plateau, and simulation experiments have confirmed the key role of the Himalaya–Tibetan Plateau in transforming regional atmospheric and oceanic circulations. Show More Summary

Global biogeography of Albian ammonoids: A network-based approach

Large-scale biogeographic provinces of Cretaceous ammonoids, as currently defined in the literature, were delimited using qualitative assessments of taxonomic inventories. Using aggregated species occurrences in the Paleobiology Database,...Show More Summary

Increased mud deposition reduces stromatolite complexity

Microbial mat growth can produce diagnostic delicate structures in low-energy environments, but mat morphology, and thus preservation of delicate structures as morphological biosignatures, is affected by mud accumulation. In Lake Joyce,...Show More Summary

Dating the Paleoproterozoic snowball Earth glaciations using contemporaneous subglacial hydrothermal systems

The presence of Paleoproterozoic glacial diamictites deposited at low latitudes on different continents indicates that three or four worldwide glaciations occurred between 2.45 and 2.22 Ga. During that time period, the first atmospheric...Show More Summary

Adeline rise

Down at the foot of Adeline Street, past Green Valley Food, past J. K’s Brickhouse, past Magnolia Oakland at 3rd Street, the road ends at the old shoreline. Where the Amtraks roll by was once coastal marsh. The geologic map uses an old pre-earthquake topographic base, so ignore the freeway and find Adeline, running through […]

The Airliner Chronicles: The San Francisco Peninsula and the San Andreas Fault

4 months agoAcademics / Geology : Geotripper

Crystal Springs Reservoir is on the upper left, while San Andreas Reservoir is on the lower right As has been no doubt obvious, I was in Hawai'i last week, and there have already been several posts about some of my adventures. I started...Show More Summary

AZGS at 3rd Annual North American Symposium on Landslides – “Slip Slidin’ Away”

Quaternary landslides (red) near I-17 in central AZ (AzSLID). Ann Youberg, Senior Research Scientist who oversees the AZGS geologic hazards group, will be participating in the North American Symposium on Landslides in Roanoke, Virginia, next week. Show More Summary

Answer to a Hawaiian Mystery, and a Cautionary Tale

4 months agoAcademics / Geology : Geotripper

If you've had a geology or earth science course, do you remember what you learned about basalt? Basalt, the low-silica volcanic rock, the one that flows instead of exploding. The one that isn't all that dangerous. Even if you haven't had such a class, you've heard that visiting volcanoes on the Hawaiian Islands is one of the things tourists can do. Show More Summary

Volcanoes, referees for the life on Earth

At the Triassic-Jurassic boundary, 200 million years ago, some 60% of species living on Earth disappeared. Scientists suspected that magmatic activity and the release of CO2 were responsible for this environmental disaster.

Bad Signs

What happens when a geologist with a Sharpie encounters wrong information on a public sign? -- Read more on

Arizona National Monuments currently under review by the Secretary of the Interior

AZGS OFR-04-2017 On 26 April 2017, President Donald Trump signed an executive order to review designations of a number of national monuments established under the Antiquities Act of 1906. Section 2 of that executive order requires the...Show More Summary

High Water Across the West: The Humboldt River at Winnemucca and Humboldt Station

When I started putting these photos together—while thinking about our last post about the Humboldt River in Carlin Canyon—I somehow (and quite erroneously) figured I could throw a whole bunch of high-water Humboldt River photos together in one blog post. Show More Summary

AZGS receives $64k to update and publish digital geologic map data

Digital geologic map for Dome Rock, Arizona The AZGS was notified last week that we will be receiving $64k from the National Geological and Geophysical Data Preservation Program, administered by the USGS, for FY18. We will be supplying the required state match, for a project total of ~$130k. Show More Summary

South Dunsmuir Ridge

I finally got to a sweet corner of town last week, the sunny side of Dunsmuir Ridge, this lovely hill in the Google Maps 3D view. The view is to the north-northwest, such that the Hayward fault runs straight up about a thumb’s width from the left edge. The maps below start with the 1915 […]

AZGS mine files spurs silver exploration in Arizona’s Plomosa Mountains

Ramsey Mine ca. 1987 Imagine a room crowded with file cabinets whose drawers are stuffed with 100,000s of pages of unpublished mine reports, correspondence, geologic maps, mine maps, drill hole data, rock chemistry, and assay results for more than 20,000 mines in Arizona. Show More Summary

Here's a Hawaiian Mystery for You: Where Did These Circles Come From?

4 months agoAcademics / Geology : Geotripper

We were on a desolate plain on the south side of Kilauea Caldera on the Big Island exploring the ongoing volcanic activity. The smoking pit of Halemaumau Crater with her bubbling lake of molten lava was only a half mile or so north of us, so yes, we were in a closed area (but legally in this instance!). Show More Summary

The True Story of the Mar-a-Lago "Sinkhole"

What really happened at Mar-a-Lago on Monday – and what to do if it happens to you. -- Read more on

A Flight Around the World's Highest Mountains: Mauna Kea and Mauna Loa

4 months agoAcademics / Geology : Geotripper

Mountains that make their own weather can be frustrating because...they make their own weather. High mountains in the path of consistent winds force air masses upwards, causing the water vapor within to condense, forming clouds and as often as not, rain. Show More Summary

High Water Across the West: The Humboldt River in Carlin Canyon — With the Carlin Canyon Unconformity!

Well, there we have it: the Carlin Canyon unconformity with the Humboldt River running nearly bankfull on April 11th of this year. Looking downstream, back toward the tunnels, we're actually still looking at the unconformity, but it's cropping out poorly on the slope below the tilted limestone beds of the Pennsylvanian-Permian Strathearn Formation. Show More Summary

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