Category Archives: USGS

USGS Mendenhall seminar: Mariana Islands seismicity & infrasound

Mendenhall Postdoctoral Research Seminar

John Lyons, USGS – Anchorage, AK

When: Monday, May 18, 2015 – 12 Noon

Where: Via WebEx and National Center, Room 3A409 (Chief Geologist’s Conference Room)


Long-period seismicity and infrasound driven by shallow magmatic degassing at Mount Pagan, Mariana Islands

Mount Pagan (570 m) is the currently active vent on the north end of Pagan Volcano, Mariana Islands.  Since the establishment of a monitoring network in 2013, a persistent degassing plume, long-period (LP) seismicity and infrasound, and infrequent small degassing explosions have dominated activity. The current low-level, open vent activity provides an ideal platform for studying the source processes of LP events, and how they relate to degassing. Many active volcanoes display LP (0.2-5 Hz) seismicity and because variations in LP activity often herald changes in eruption behavior, understanding the source mechanisms that generate LP events is a primary goal of volcano seismology. Expanding observations to include other data types greatly facilitates the interpretation of LP events. Studies correlating seismic and infrasound data have revealed important linkages between shallow LP seismicity and the generation of LP infrasound at other open vent, basaltic systems. Some form of degassing often accompanies LP activity, and integrating seismic and infrasound data with plume observations or gas chemistry allows further refinement of source models. In this study, we focus on characterizing the LP activity and interpreting the source processes generating the seismic and infrasonic signals through waveform modeling. The results are combined with gas emission and composition data and information about the shallow geologic structure to develop a model of shallow degassing for Mount Pagan.

WebEX Info

Topic: Mendenhall research Seminar
Date: Monday, May 18, 2015
Time: 11:00 am, Eastern Daylight Time (New York, GMT-04:00)
Meeting number: 714 351 061
Meeting password: (This meeting does not require a password.)
Host Key: 237217

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Teleconference: National Center in Reston, VA Dial In: x4848
DOI Dial In Number: 703-648-4848
Non-DOI Toll Free Dial In Number: 1-855-547-8255*
Security Code: 91930 followed by the # sign

Seth Burgess at USGS Reston: magmatism and mass extinctions

Special Seminar

Seth Burgess*, USGS – Menlo Park, CA

* Recipient of the 2014 Cozzarelli Prize (

When: Monday, April 27, 2015 – 11 AM

Where: Via WebEx and National Center, Room 1C400 (Visitor Center)


Using high-precision geochronology to test the link between magmatism and mass extinction

Broad temporal coincidence between select Phanerozoic instances of mass extinction and large igneous province (LIP) magmatism has led many to hypothesize a causal link between the two. Testing the plausibility of this connection depends on the tempo of both and their relative timing. Thus, dating the records of mass extinction and magmatism with the maximum possible precision and accuracy is critical. This presentation will detail the application of U/Pb thermal ionization mass spectrometry (TIMS) geochronology to (1) volcanic ash beds intercalated with the fossil record of the end-Permian mass extinction, and (2) lava flows, sills, and pyroclastic rocks of the Siberian Traps LIP. New dates permit a revised calculation of the tempo of magmatism and mass extinction and allow resolution of their relative timing.

WebEX Info

Topic: Mendenhall Fellow Talk: Seth Burgess

Date: Monday, April 27, 2015
Time: 10:30 am, Eastern Daylight Time (New York, GMT-04:00)
Meeting number: 719 125 959
Meeting password: (This meeting does not require a password.)
Host Key: 819447

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Teleconference: National Center in Reston, VA Dial In: x4848
DOI Dial In Number: 703-648-4848
Non-DOI Toll Free Dial In Number: 1-855-547-8255*
Security Code: 91930 followed by the # sign

Mendenhall seminar @ USGS: Quakes on Wasatch Fault

Mendenhall Postdoctoral Research Seminar

Scott Bennett, USGS – Golden, CO

When: Wednesday, March 4, 2015 – 12 Noon

Where: Via WebEx and National Center, Room 1C400 (Visitor Center)


How Big and How Frequent Are Earthquakes on the Wasatch Fault in Utah? Using Paleoseismology and Lidar to Evaluate Earthquake Rupture Patterns

The 350-km-long Wasatch fault zone (WFZ) consists of ten west-dipping normal fault segments at the eastern boundary of the Basin and Range Province, Utah. Fresh fault scarps at the foot of the Wasatch Mountains indicate that large earthquakes have recently occurred on the WFZ, as first documented by G.K. Gilbert in the 1880s. The most recent earthquake predates written records and European settlement in the 1840s, leaving paleoseismologists to the tasks of determining the size and frequency of past earthquakes and estimating the current seismic hazard. Over three decades of paleoseismic trench research having produced abundant earthquake timing data along the central WFZ. These data have been interpreted as evidence for ruptures during large (M≥7.0) Holocene (<11 ka) earthquakes that were restricted to a single fault segment. However, uncertainties in earthquake timing permit earthquake correlations that allow for longer ruptures that spanned segment boundaries. To improve rupture length estimates and evaluate the persistence of Holocene rupture termination at central WFZ segment boundaries, a collaborative team from the USGS and the Utah Geological Survey conducted four paleoseismic trench studies near these boundaries. Data from paleoseismic trenches constrain the timing and surface displacement of Holocene earthquakes and, when integrated with results from adjacent trenches, provide new constraints on surface rupture length and earthquake magnitude. We have also analyzed new high-resolution (8 pts/m2) airborne lidar data along the central WFZ, which provide unprecedented elevation information for lake shoreline features associated with late Pleistocene Lake Bonneville. These faulted shoreline features serve as strain markers across the WFZ, permitting precise fault offset estimates near WFZ segment boundaries for the past ~10­–20 kyr. I will summarize paleoseismic and geomorphic constraints on the extent of recent surface-rupturing earthquakes and evidence for non-persistent rupture terminations at segment boundaries along the central Wasatch fault zone. These findings will permit a more accurate characterization of the earthquake hazard in the Wasatch Front region.

WebEX Info

Topic: (20) Mendenhall Seminar: Scott Bennett
Date: Wednesday, March 4, 2015
Time: 12:00 pm, Eastern Standard Time (New York, GMT-05:00)
Meeting number: 711 911 008
Meeting password: (This meeting does not require a password.)
Host Key: 819057

Click the following link to view or edit your meeting information, or to start your meeting.

Teleconference: National Center in Reston, VA Dial In: x4848
DOI Dial In Number: 703-648-4848
Non-DOI Toll Free Dial In Number: 1-855-547-8255*
Security Code: 91930 followed by the # sign

Oh Shenandoah! 80,000 Years of Climate Change in Virginia’s Great Valley

Mendenhall Postdoctoral Research Seminar and 

Eastern Geology and Paleoclimate Science Center Seminar

Benjamin Hardt – USGS, Reston, VA

When: Tuesday, May 13, 2014 – 12 Noon

Where: National Center, Room 1C400 (Visitor Center)


Oh Shenandoah! 80,000 Years of Climate Change in Virginia’s Great Valley

Rapid climate change events such as the Younger Dryas, Dansgaard-Oeschger (D/O) events and Heinrich stadials are a prominent feature of climate during the last glacial period. Corresponding to large temperature changes in Greenland and the North Atlantic, these abrupt shifts have notable consequences for European temperatures, the Asian summer monsoon, and South American precipitation. Very little is yet known about the extent of variability associated with these events in the eastern United States.  A precisely dated record from two stalagmites collected from Grand Caverns in Grottoes, Virginia, provides strong evidence of the Younger Dryas and earlier D/O events impacting the eastern United States.  While these events may be associated with regional temperature change, the stalagmite record likely represents a more direct response to changes in the composition of annual recharge. Available drip water data indicate minimal seasonal variability in δ18O, suggesting mixing times of ~12 months or longer. Changes in the seasonal balance of precipitation between winter- and summer-dominated regimes could explain the observations, although additional study is needed. The strong expression of millennial events in δ18O from the Grand Caverns stalagmites demonstrated by wavelet analysis of the time series contrasts with results from West Virginia, which show minimal variability at millennial scales, and large changes associated with orbital forcing. The stronger expression of millennial events at Grand Caverns is likely due to its position on the east flank of the Appalachians, allowing a greater contribution of Atlantic moisture, particularly during winter months.


WebEX Info

Topic: Mendenhall/EGPSC Seminar-Ben Hardt
Date: Tuesday, May 13, 2014
Time: 11:30 am, Eastern Daylight Time (New York, GMT-04:00)
Meeting number: 714 367 066
Meeting password: EGPSC

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Mendenhall research seminar: Magma evolution at Yellowstone

Mendenhall Postdoctoral Research Seminar

Christy Till, Volcano Science Center, USGS-Menlo Park, CA

When: Wednesday, September 18, 2013 – 12 Noon

Where: National Center, Room 4C315


Quantifying Time Scales of Magma Evolution at Yellowstone Caldera

Caldera-forming eruptions represent the most catastrophic volcanic events and pose the greatest volcanic hazard on Earth. Yet the rate at which this type of volcano amasses voluminous rhyolite magma in subsurface magma chambers and their eruption-triggers is poorly constrained.  Dr. Till will present new results on the time interval between the thermal rejuvenation and eruption of magma during the youngest episode of effusive volcanism at Yellowstone Caldera using ultra high-resolution ion-microprobe (NanoSIMS) diffusion dating, radioisotopic dating, and chemical analyses of single crystals.

She will focus on the youngest of the Upper Basin Member intra-caldera effusive rhyolite lavas, the Scaup Lake flow (SCL), which erupted ca. 257 ka after a volcanic hiatus of approximately 200 k.y. The SCL contains zoned phenocrysts of quartz, clinopyroxene, orthopyroxene, plagioclase, and sanidine with accessory zircon and Fe-Ti oxides that show petrographic evidence for magmatic recycling of plutonic crystals.  SCL clinopyroxene commonly exhibit exsolution lamellae in their cores, signifying that subsolidus conditions were attained during the early evolution of these rhyolites.  Results from U-Pb dating indicate that the SCL magma experienced initial crystallization in the Yellowstone reservoir ca. 350 ka followed by subsequent rejuvenation ca. 240 ka.  The crystal chemistry and sanidine and pyroxene diffusion dating indicate that the Yellowstone magma chamber which sourced the SCL was heated and rejuvenated ~1000 years prior to eruption.  Together these techniques and observations imply millennial timescales for the rejuvenation of silicic intrusions and the generation of eruptible magma at Yellowstone.

WEBEX info:

Teleconference: National Center in Reston, VA Dial In: x4848
DOI Dial In Number: 703-648-4848
Non-DOI Toll Free Dial In Number:1-855-547-8255
Security Code: 91930 followed by the # sign

For help with WebEx:
– Visit, click USGS Help (on left)

Hardt on Bermuda High @ USGS Reston


Changes in Summer Precipitation in the Eastern US: a short history of the Bermuda High


 Ben Hardt

 USGS – Reston

Eastern Geology and Paleoclimate Science Center

 12 Noon, Wednesday, June 5, 2013  

USGS Visitor’s Center Auditorium

(bring your lunch if you wish)

CONTACT: Dr. Daniel Doctor (

Mendenhall special seminar: the MiniSipper


MiniSipper: A New Concept for High-capacity, Long-duration, Automated In Situ Water Sampling

Presenter: Thomas Chapin of the USGS Denver office

Friday, June 14, 2013 at 10 AM

USGS Visitor Center (Reston: National Headquarters), 1C400

MiniSipper: A New Concept for High-capacity, Long-duration,

Automated In Situ Water Sampling

Thomas Chapin

(Former Mendenhall Fellow)

Crustal Geophysics and Geochemistry Science Center, Denver, CO

Most environmental water quality monitoring studies rely on hand-collected “grab” samples for water sample collection. However, grab sampling is expensive with significant costs for personnel, equipment, vehicles and travel. Field costs can be especially high if the sampling site is remote, dangerous to access, or snowbound for many months of the year. Grab sampling typically provides a few samples per year and this low temporal resolution sampling rarely captures the details of major transient hydrologic processes such as storm, flood, or seasonal runoff events. Currently available automated samplers could provide water sampling at remote sites, but these samplers are typically large, heavy, collect 24 one liter samples, and are not well suited for operation in freezing conditions.

The USGS has developed a small, light, low-cost, high-capacity, in situ water sampler, the MiniSipper, to overcome the limitations of current automated water samplers. The MiniSipper injects 2 to 10 mL discrete or integrated water samples into a 500’ Telfon sample coil. Nitric acid is added to stabilize each sample and individual water samples are then separated with a gas bubble. Over 250 five mL water samples can be collected with <5% carryover. The MiniSipper collects samples in situ for up to 12 months unattended and even operates under ice for over-winter sampling. After recovery, samples are pumped out of the sample coil and analyzed by high sensitivity multi-element methods such as ICP-MS.

The MiniSipper provides long-duration high-resolution metal data for hydrologic and geochemical processes that are almost impossible to observe with currently available sampling methods. MiniSipper technology is very flexible and MiniSippers has been used for acid mine drainage studies (above and below ground), tracer studies (above and below ground) and for post-wildfire runoff studies. The Borehole MiniSipper is designed for well monitoring, fits down a 2” borehole, and collects weekly samples over an entire year. The MiniSipper has primarily been used for metal analysis but this technology should be applicable to other analytes of interest such as organics, pesticides, nutrients, etc. This presentation will: 1) give an overview of the MiniSipper instrumentation; 2) present results from high-resolution acid mine drainage and post-wildfire monitoring; and 3) discuss applications currently under development such as the Event Response MiniSipper and the Disaster Response MiniSipper. Bring your sampling needs, ideas and problems; perhaps the MiniSipper could offer a solution.