Arizona Geology Blog

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blog of the State Geologist of ArizonaLee Allison
Updated: 33 min 43 sec ago

AZGS Chief Geologist, Jon Spencer, retires after 33 years

Sun, 2015-11-22 11:00
Dr. Jon Spencer, Chief Geologist at AZGS, and head of the geological mapping program, retired on Friday after 33 years with the Survey.   We had an informal luncheon honoring Jon, with a small number of family, friends, and colleagues,  to thank Jon for his many contributions.   [Right, Jon - center- is flanked by former State Geologist Larry Fellows, left, and Steve Reynolds, professor of geosciences at ASU, right, who were instrumental in hiring Jon to the Survey's predecessor agency at the University of Arizona.  Photo by Stephanie Mar]

Jon's last geologic map, "Geologic map of the Cross Roads 7.5' Quadrangle and the southern part of the Gene Wash 7.5 Quadrangle," was officially released on Friday as an AZGS publication and it was formally dedicated to Jon in recognition to the understanding of the geology of Arizona.

Under Jon Spencer's leadership, the AZGS mapping program became one of the premier efforts in the country, often held up as a model for other states.     [Bottom, Jon listens to colleagues commenting on his contributions.  A framed copy of Cross Roads map dedicated to him stands at the right.  In front of him is a 1 to 12 scale photo of him in the field, mounted on cardboard, with multiple copies offered by Brian Gootee to the other mapping geologists to take with them to the field, so they also have Jon along with them.]

Citation: Spencer, J.E. and others, 2015, Geologic map of the Cross Roads 7.5' Quadrangle and the southern part of the Gene Wash 7.5 Quadrangle, La Paz County, Arizona, and San Bernardino County, California. Arizona Geological Survey Digital Geologic Map DGM 111, 1 map sheet, 1:24,000 scale.
Categories: AZGS Web Posts

More small quakes on the Intermountain Seismic Belt

Sun, 2015-11-22 10:42
There was yet another small quake in northwest Arizona, along the southern end of the Intermountain Seismic Belt [right, red lines are active faults]. This magnitude 1.8 event [blue dot in image] occurred at 4:04 p.m. on Friday, following two others [yellow dots in image] just before noon in the region.   Another tiny quake at magnitude 0.9, [orange dot in image] occurred this morning, at 2:10 a.m

Dr. Jeri Young, who runs the state seismic network for AZGS cautions that the preliminary locations from the USGS are off by 5-10 km, when the Arizona stations data are incorporated.
[Map credit, USGS]

Categories: AZGS Web Posts

Two more small quakes in northwest Arizona

Fri, 2015-11-20 16:06
 Northwest Arizona had its fifth and sixth small earthquakes in the last week and a half, today just before noon. A magnitude 2.9 event at 11:48 a.m., local time was followed ten minutes later by a magnitude 1.5 quake very close by that was likely an aftershock.    The events occurred about 33 miles southeast of Littlefield, Arizona, and are in the same area as a magnitude    quake that occurred on November 14.   [Right, the epicenters of today's quakes are in orange. Last week's event in yellow. Red lines on are faults. Credit, USGS]

The quakes are in the midst of a number of active faults that comprise the southern end of the Intermountain Seismic Belt and close to the Washington fault.

Categories: AZGS Web Posts

4th small quake in northwestern Arizona this week

Tue, 2015-11-17 15:13
We've had a small spate of small quakes in the northwest corner of the state this week with the fourth one occurring at 7:53 a.m, yesterday.    The earthquakes are still widely scattered and do not appear to be related.  The latest one was 17 miles south-southeast of St. George, Utah. [Right, the latest quake epicenter shown in blue.   The week's previous quakes are in yellow. Credit, USGS]

Categories: AZGS Web Posts

2 million page views

Mon, 2015-11-16 18:56
This blog passed the 2 million page views level today, so thanks to all of you readers.   It probably passed that point some time ago, but I did not start tracking analytics until a year into blogging.   

I've made over 4,100 posts since beginning, but this past year my blogging has dropped off precipitously.    That is a factor of being over-committed on projects, and a recognition that more viewers visit our Facebook page run by Mike Conway.  The Facebook page is actually better suited for a lot of the more regular announcements that I used to post here.

Our Facebook page also reaches out to a larger more diverse audience. Arizona Geology is still targeted to the geoscience community.    But I've also heard from a number of news reporters who follow the site to catch items that would be good stories.  

 So, onward!

Categories: AZGS Web Posts

New interactive map of Arizona wineries, vineyards, and tasting rooms

Mon, 2015-11-16 16:31
Arizona's burgeoning wine industry is now showcased in a new online interactive Wine Trail Map, built here at AZGS as part of a new Arizona Wine Country page on the Arizona Experience website.

Three regions in Arizona are growing grapes for wine: Sonoita in Santa Cruz County, Willcox in Cochise County, and the Verde Valley in Yavapai County. View the Arizona’s Wine Trail Map.

The map shows wineries, vineyards, and tasting rooms in all three areas.    Each location has contact info, description of the wines, history of the facility, directions, and photos.  [Below, screen shot of the Alcantara Vineyards pop-up.  The writeup continues below what is visible in this clip.]

Categories: AZGS Web Posts

Three small quakes in northwest Arizona last week

Mon, 2015-11-16 07:32
Three small earthquakes were recorded widely scattered across northwest Arizona in recent days [right, yellow dots show epicenters of quakes recorded last week. Credit, USGS].

A magnitude 1.6 quake occurred on November 11, about 19 miles east-southeast of Boulder City, NV.

A magnitude 1.3 event occurred on November 13 about 21 miles south of Colorado City.

A magnitude 1.4 quake occurred on November 15 about 34 miles southeast of Littlefield.

There are no reports of any of these being felt.   It's also unlikely that they are linked geologically.

Categories: AZGS Web Posts

My op-ed on geologic hazards published in Arizona Republic

Sun, 2015-11-15 11:23
The Arizona [Phoenix] Republic newspaper published my editorial piece today on geologic hazards in Arizona.  This was prompted by the Black Canyon City earthquakes on November 1 which were felt over much of central Arizona.  The online version  - - has additional photos, videos, and live links to many of the geologic events I reference in the article.  [Right, earth fissure in the Queen Creek area, 2006. Credit, Bryan Macfarlane, AZGS]

I concluded that "We have only to look around us at the dramatic landscapes of Arizona to appreciate the power of natural events that throw up mountains and volcanoes, carve immense canyons and constantly sculpt the land beneath our feet.
The geologic forces that created Arizona also create hazards and risks for us. Recent earthquakes are just one reminder of that." Last weekend I also did a live radio broadcast (KTAR, Phoenix and syndicated statewide) with Rosie Romero, host of "Rosie on the House" talking about earthquakes and landslides.   The show is podcast at, in Segments 3 and 4.

Categories: AZGS Web Posts

Aftershock from Black Canyon City quake felt in area

Wed, 2015-11-04 19:48

A magnitude 2.2 earthquake occurred last night at 8:33 p.m. about 13 miles north of Black Canyon City, Arizona, according to Jeri Young who manages the states seismic monitoring network at AZGS. We received reports from ranchers in the area who felt the ground shaking. This is the fourth felt event in the area over the past several days. This is likely an aftershock to the largest event, a magnitude 4.1 quake at 11:29 p.m. last Sunday evening, which was felt over a large area of the state and rattled the entire Phoenix metro area.   

The 2.2 event is the northernmost event on this map. (North is to the top of the map.)

Categories: AZGS Web Posts

Arizona earthquake funding denied

Tue, 2015-11-03 07:56
The USGS turned down our funding request to characterize the most active fault in Arizona to better understand earthquake hazards.   Ironically, the letter informing us that the proposal was denied, arrived just hours after a series of earthquake shook most of the population of the state.

AZGS proposed doing detailed work on the Lake Mary fault in northern Arizona under the National Earthquake Hazards Reduction Program.  The letter from the USGS program manager stated:
Your proposal ... has been recommended for funding by the peer panel that reviewed the proposed research. Unfortunately, the U.S. Geological Survey (USGS) Earthquake Hazards Program does not have sufficient resources available to fund your proposal in fY 2016. Of the 211 proposals reviewed under this Announcement, the U.S. Geological Survey (USGS) will support 39 proposals; will place 39 proposals on hold pending a funding decision in January 2016; will decline to fund 52 proposals due to a lack of sufficient funds; and will decline to fund $1 proposals that were not recommended for funding by the peer panels. Arizona suffers from a widespread perception that we don't have earthquakes and thus are low on the priority list for resources to address this hazard and risk to the population.
Categories: AZGS Web Posts

4.6 million Arizonans shaken by quakes

Mon, 2015-11-02 18:56
More than 4.6 million Arizonans live in the areas where people felt the ground shaking from last nights earthquakes near Black Canyon City, according to information posted by Ramon  Arrowsmith, ASU geology professor, on his "Active Tectonics" blog -  The estimate comes from the USGS.

Ramon's added a number of links to relevant background materials and made the observation that "the mapped active faults to the east (Horseshoe, Carefree, and Sugarloaf--all similar orientation."    We have not yet processed the first motions of the quakes to see what type and direction of movement is associated with the ruptures, and whether they correlate with the rough north-south alignment of the epicenters.

Ramon posted seismograms of the three events as recorded at ASU (right).

Categories: AZGS Web Posts

Reference materials for Black Canyon City quakes

Mon, 2015-11-02 10:34
The following online maps and reports are getting lots of attention in the wake of the three earthquakes last night - M3.2,M4.1, & M4.0 - near Black Canyon City, about 45 miles north of Phoenix.   All of these are online for free viewing or downloading.

Pearthree, P.A., 1998, Quaternary Fault Data and map for Arizona. Arizona Geological Survey Open File Report, OFR-98-24, 1 map sheet, map scale 1:750,000, 122 p.
Pearthree, P.A., 2011, Big Chino Fault, Chino Valley, Arizona - Video. Arizona Geological Survey Open File Report, OFR-11-08, 6-minute video. The video is published at the Arizona Geological Survey's azgsweb's YouTube channel. 
Conway F.M. and Young, J.J, 2012, Arizona is Earthquake Country. Arizona Geological Survey Down to Earth DTE # 21, 44 p.
Leighty, R.S., 2007, Geologic Map of the Black Canyon City and Squaw Creek Mesa Area, Central Arizona: Arizona Geological Survey Contributed Map CM-07-A, map scale 1:24,000, 46 p. and 1 map sheet.
Ferguson, Charles A., Haddad, David E., Johnson, Brad J., Guynn, Jerome L., Spencer, Jon E., Eddy, David L., and Clark, Ryan J., 2008, Geologic Map of the east half of the Black Canyon City 7.5’ Quadrangle and the west half of the Squaw Creek Mesa 7.5’ Quadrangle, Maricopa County, Arizona: Arizona Geological Survey Digital Geologic Map DGM-64, version 1.0, map scale 1:24,000, 27 p. and 1 map sheet.
Categories: AZGS Web Posts

Black Canyon City Earthquake Sequence

Mon, 2015-11-02 09:53

The Arizona Geological Survey (AZGS) and Northern Arizona University operate several seismometers throughout the state.  Using 15 stations, 5 of which are not currently used by the National Earthquake Information Center run by the USGS, AZGS has refined the locations for the foreshock, mainshock and the large aftershock from the November 2nd[using UTC time - using local time, the events were on Nov. 1] Black Canyon City sequence of quakes (Table below).  The M3.2 foreshock was located at approximately 5km north of Black Canyon City at a very shallow depth, between 1-5km.  The mainshock was located approximately 18km NNE of Black Canyon City and occurred at approximately 11km depth.  The largest aftershock an Mw 4.0 occurred only 20 minutes following the mainshock at a depth of approximately 5km.  There have been multiple smaller aftershocks, but there are not enough seismometers close enough to the area of the sequence to accurately locate them.  The closest station is located near Payson at about 65km, with the Wickenburg station being 88km away.   
The closest known active fault is the Horseshoe Fault, located 35km SSE of the mainshock.  The Black Canyon City Sequence has not generated a quake large enough to break the surface.  Aftershocks will continue for several months or longer. 
The table below lists the revised locations, and the extent of possible errors in location, horizontally (ERH) and vertically (ERZ).

Mw Time -UTC Date Lat Long Depth (km) RMS(Seconds) ERH(km) ERZ(km) 3.2 03:59.33 11-02-15 34.11016 -112.1460 <1 .0="" p=""> 0.16 1.05 5.27 4.1 06:29.66 11-02-15 34.23350 -112.12366 11.2 0.07 1.01 3.18 4.0 06:49.32 11-02-15 34.17950 -112.08633 5.19 0.10 0.83 2.77
Post from Dr. Jeri Young, AZGS
Categories: AZGS Web Posts

Black Canyon City quake locations refined; seismograph recording posted

Mon, 2015-11-02 09:38
We have updated the locations of last nights earthquakes near Black Canyon City, using the Arizona seismic stations in the  AZGS network.

Jeri Young also passed along this shot of the seismic signals received by the nearest station in our network, Strawberry/Payson X16A, about 65 km east of last night's quakes.   All three of the bigger quakes, M3.3, M4.1 and M4.0, are easily visible by the red waveforms at their start.

Categories: AZGS Web Posts

Earthquakes north of Black Canyon City shake up much of Arizona

Mon, 2015-11-02 06:21

Notable earthquakes with magnitudes of 4.0 and 4.1 hit a few miles north of Black Canyon City around midnight Sunday, with a foreshock of magnitude 3.2 at 9 pm [top, location map from USGS]   Dr. Jeri Young, who manages the seismic monitoring network run by AZGS, calculates that the location of the mainshock is a few miles further north than reported by the USGS, using information from Arizona stations closer to the events [bottom].

Reports are coming in that the two big shocks were felt from the Grand Canyon to Tuscon and widely across the region [center map.  Source, USGS]

 The M4.1 quake struck at 11:29 pm, local time, with the 4.0 quake hitting at 11:49 pm, Sunday, November 1.    Smaller aftershocks are being recorded although they have been too small to be felt.

Categories: AZGS Web Posts

Meteor breakup over Tucson

Sat, 2015-10-31 06:08
Heading off to the airport this morning at 5:18 a.m. I watched two bright lights in the southwest sky moving to the southeast.   The front light was orangish and the rear one yellow.     They were moving faster than planes normally do which is when I realized the pair were meteorites on the same path.  Probably one meteorite that broke up as it entered the atmosphere.

But they were moving slower than most meteorites that I've seen.   Normally the little ones I see leave a brief streak and are gone.  Not this pair.   I kept thinking that if they really are meteorites, they should burn up quickly  The trailing one burned out after a few more seconds and the leading one continued for a number of seconds beyond that.

Tres cool!
Categories: AZGS Web Posts

New report on Cordilleran tectonics likely to generate its own upheaval

Wed, 2015-10-28 19:57

A new paper published today is bound to generate heated debate.    Tucson-based geologist Robert "Bob" Hildebrand's article "Dismemberment and northward migration of the Cordilleran orogen: Baja-BC resolved" came out in GSA Today with a provacative conclusion.   Bob proposes that the sinistral Texas Lineament and the sinistral Lewis & Clark transverse zone, located about 1300 kilometers to the north, can be restored to one through-going zone. [Right, Figure 2 from the paper.  The proposed fault is shown in green extending across the entire N-S extent of the US.]

The proposed right-lateral fault divides the Basin & Range province from the Colorado Plateau across the extent of Arizona and Utah and well into Canada.

Bob's previous alternative tectonic theories have drawn a lot of attention and animated discussion.  This one is going to do the same.

Categories: AZGS Web Posts

Debris flows (mudslides) worsened by wildfires - expect more across the West

Sat, 2015-10-17 18:08
Yesterday's mudslide (actually debris flows) on Interstate 5 in southern California were a result of a huge El Nino storm over grounds laid bare by intense wildfires and hardened to runoff by drought.

With predictions of the biggest El Nino of the century and large tracts of lands having been burned, we may expect more such events across the West, including possibly here in Arizona.  [Right, photo credit CalTrans]

California agencies have been warning of debris flows from burned areas for several months.    On Wedesday, Cal Fire warned that they had identified 133 'mudslide danger zones' in northern California, most associated with the Valley fire in Lake and Amador counties.
Categories: AZGS Web Posts

"Geology of Northern Arizona" guidebooks now online

Wed, 2015-10-14 16:20

AZGS has posted online for free viewing and downloading "The Geology of Northern Arizona - With Notes on Archaeology and Paleoclimate" at   This is a two volumes set comprising 800 pages of illustrated field trip guides for sites in Northern Arizona that was published in 1974 as part of the Rocky Mountain section meeting of the Geological Society of America.

For the first time it is available online as downloadable PDF.

Northern Arizona has attracted pioneers in North American geology since the days of John Wesley Powell; when northern Arizona was considered to be a part of our "last frontier." Perhaps Powell, Darton, Dutton, Walcott, Noble, Gregory, Gilbert, Davis, or Robinson would not have been surprised to learn that the geology of northern Arizona would play an important part several generations later in the geologic exploration of a new frontier--that of space.

AZGS thanks GSA, the Museum of Northern Arizona, and Northern Arizona University for graciously providing permission to put this online.

The two volume set was scanned and processed by Kevin Horstman. Thanks Kevin!

[excerpted from the AZGS announcement]

Categories: AZGS Web Posts

National Monument bill aimed at preventing mining in northern Arizona

Wed, 2015-10-14 14:37
 Tucson congressman Raul Grijalva introduced legislation to put 1.7 million acres in northern Arizona off limit to mineral exploration and mining by creating the Greater Grand Canyon Heritage National Monument.  [Right, credit, Grand Canyon Wildlands Council]

In a news interview, Rep. Grijalva admitted the bill has no chance of passage in the House and likely won't even get a hearing but he hopes President Obama will intervene and use the Antiquities Act to declare a national monument without requiring congressional approval.

The land proposal had previously been called the Grand Canyon Watershed National Monument.

Northern Arizona hosts a huge uranium resource, mostly in breccia pipe deposits.   A recent study by AZGS found that the number of breccia pipes and consequent  uranium resources are likely to be at least 10 times greater than previous studies.

A report released last week by the US Dept. of Energy's Energy Information Administration revealed that US nuclear energy producers doubled the amount of uranium they bought from Kazahkstan last year, while US sources dropped dramatically.

Categories: AZGS Web Posts