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Sibley sights: Lapilli tuff

Sibley Volcanic Regional Preserve is the site of a small volcanic center that was last active about 10 million years ago. After it fizzled out, the whole thing was gradually buried in younger sediment. Within the last few million years, the action of the Hayward fault squeezed, folded and uplifted this sequence of rocks and […]

A Salute to Cassini-Huygens and the Team Who Successfully Explored Saturn for More Than a Decade

Amid the stupidity emanating from Washington D.C. these days, depression can be a real impediment to a happy life. Other events unrelated to politics give me some sense of hope about the future of humanity, and one of those things is drawing to a close this week: the Cassini-Huygens mission to Saturn. Show More Summary

AZGS STATEMAP 2017 deliverables: Delivered!

We just delivered geologic map data for four 7.5’ quadrangles to the US Geological Survey as part of our 2017 STATEMAP work – see the list below. Before releasing the map and GIS database publically, the authors will make any necessary revisions, polish the map appearance and the legend for consistency with AZGS standards. Show More Summary

Wandering Amongst the Granite Knobs in the Northern Sierra

Granitic knobs in the northern (way northern) Sierra. It's been a busy summer, such that I really haven't had time to get much blogging done—and I had so many good posts planned! But it's been really difficult for me to do much of anything...Show More Summary

Tour of the Fan: Lobe 4

During the eight years I was surveying every sidewalk in Oakland, taking in the geology and geography as I went, I took thousands of pictures. Here’s a baker’s dozen of my favorite shots from the ancient alluvial fan that dominates central Oakland, specifically the large segment I call lobe 4. Every part of the Fan […]

The Worst Natural Disaster in U.S. History: It wasn't last week, and it won't be this week either

Source: National Weather Service I was doing a quick search for information on the United State's worst ever natural disaster, and found almost immediately that today is the anniversary of that event. That might sound a bit strange, since the media is describing the devastation of Hurricane Harvey as the worst U.S. Show More Summary

Modeling Post-Wildfire Debris-Flow & Flooding Assessment: Coconino County, Arizona

Cover shot of AZGS Open-File Report Over the past decade the Southwestern U.S. has seen a surge in the number and intensity of wildland fires. In Arizona, wildfire season overlaps with the annual monsoon, resulting in post-wildfire debris flows and floods that threaten life and property. Show More Summary

An early look at the Fan

Lots of people love old photographs of familiar places, or old landmarks when they were new. I love old photos of Oakland because they show the land before it was paved over and/or forested. The early California photographer Carleton Watkins was instrumental in saving Yosemite as a public park, simply because his large-scale images let […]

Time Heals All Wounds. Or Does it Just Hide Them? The Ghosts of Nelder Grove (Reposted)

According to news reports, the Railroad Fire in the Sierra Nevada has reached the Nelder Grove of Sequoia Trees. It's uncertain what the outcome will be, as the trees are adapted to wildfires, but less so when the forest surrounding the trees is overgrown and stressed by five years of drought. Show More Summary

Disasters Abound - But You Can Make A Difference

South Asia, Sierra Leone, and southern Texas are experiencing catastrophic flooding and landslides. Here's how to help. -- Read more on

Return of Arizona Mining Review: Mining Pozzolan in Central Arizona

Volcanic tuff pozzolan exposed at Kirkland Mine Return of Arizona Mining Review Following a 15-month hiatus, the Arizona Mining Review (AMR) filmed and its 40 th episode, Pozzolan mining in central Arizona, on 28 Aug 2017. The Arizona Geological Survey’s Geologic Extension Service launched the Review in Jan. Show More Summary

Houston's Horrific Flooding: Thank Goodness It Can't Happen Here...Eh...Right? Think Again...

What's happening in Houston is beyond belief. And tragically, horrible flooding is happening now in southeast Asia as well, with at least 1,200 people dead. Although the extent of the damage in Houston is not yet known, meteorologists are already calling it unprecedented in American history. Show More Summary

M3.3 Earthquake & aftershocks in northwestern-most Arizona

M3.3 Earthquake & 7 aftershocks (8/28/2017) At 7:03 a.m. on 28 August, a magnitude 3.3 earthquake occurred in the northwest corner of Arizona about 20 miles SSE of Mesquite, Nevada. Seven smaller aftershocks followed on the heels of the initial event (Table 1, Figure 1). Show More Summary

The Trump Administration's Effect on National Parks

It's been a hard summer for our public lands. -- Read more on

A stroll up Indian Gulch, or Trestle Glen

Once upon a time there was a thriving native encampment near the head of San Antonio Slough, tucked under bountiful oak trees in a valley with a permanent stream. Then the padres of New Spain put the natives behind walls to earn their bread with the sweat of their brows, and a generation later the […]

Hope and Willful Ignorance: Why I'm Going to Work This Week

There's road rage. There rage tweeting. And I guess there is rage blogging. I know this because I'm doing it tonight. I'm filled with rage, and feeling somewhat helpless to do anything about it. And yet there is always something that...Show More Summary

The Amazing Disappearing (and Very Dangerous) Mountain: Mt. Rainier

Yes, disappearing. In two senses, one rather personal. Mt. Rainier is actually one of the most obvious, most visible mountains on planet Earth. At 14,411 feet (4,392 meters), it towers over western Washington, and in clear weather can be seen from more than a hundred miles away in some directions. Show More Summary

Wonders of the Eclipse

Marvels happen even when you aren't in the path of totality! -- Read more on

Just Barely Through the Fog Banks: The Eclipse from Ground Zero, the Oregon Coast

Yeah, I was really taking a chance, choosing to stay on the Oregon Coast for the 2017 eclipse. The reason? The fog. And there was a lot of it. To make the long story short, it never really lifted, but we could still see most of the sights through the clouds. Show More Summary

Well water in use

Once upon a time, we used to produce a lot of our water from local wells, but for the last century we’ve retired them as the aquifers were drawn down or polluted. So I’m always surprised and intrigued to see wells still at work. This is on Willams Street in San Leandro. The location is […]

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