Category Archives: USGS

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

Please click the link below to see more information, or to join the meeting.

Although no login account is required to use Webex to attend
a meeting, you will need to supply your name, email address,
and a meeting password (if provided) to join the meeting.

When it is time to attend the meeting, please visit this link:

Teleconference: At start time of the conference, each location must call one of the dial-in numbers:
From the National Center in Reston, dial internally x4848
From all other USGS/DOI locations, dial 703-648-4848
From nonDOI locations, dial toll free 855-547-8255
The toll free number is provided as a courtesy for use by attendees that are working offsite. This number is blocked at most DOI locations, due to the fact that is it less expensive to dial over FTS. If you are unable to connect with the toll free number for any reason, please use 703-648-4848.

After the voice prompt, please enter the Conference Security Code 88002010 followed by the # key. You will hear a tone confirming that you have successfully joined the conference call. If you weren’t successful, you will hear another voice prompt with instructions.

If you are disconnected for any reason, please dial in again using the instructions listed above.

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.

Wech on “Slow Slip, Megathrust Earthquakes, and Subduction Zone Dynamics” @ USGS

Aaron Wech will be giving a talk on “Slow Slip, Megathrust Earthquakes, and Subduction Zone Dynamics” on Friday, May 17, 2013, at 10:00 am in Room 3A409 (Chief Geologist’s CR) at the USGS National Headquarters in Reston.

Aaron is a new Mendenhall Fellow who began his postdoctoral research at the Alaska Volcano Observatory in February.

Please pass on this information to anyone that may have an interest in the topic.


Need Details? Ask Rama Kotra, E-mail:

Jahns Distinguished Lecturer at USGS: Mountains falling apart

The Mountains Are Falling Apart; A Spectrum of Mass Failures from Landslides through Deep-Seated Gravitational Spreading (Sackung), to “Unfolding” of Folds
James P. McCalpin, GEO-HAZ Consulting, Inc.

Dallas Peck Auditorium – USGS National Headquarters in Reston, VA
Monday March 18, 12:00

Mendenhall Postdoc talk: plant response to climate across North American deserts

Mendenhall Postdoctoral Research Seminar

Regional signatures of plant response to climate across North American deserts: forecasts for DOI management and planning

Seth Munson, Southwest Biological Science Center, Denver, CO

When: Wednesday, February 20, 2013 – 1 PM

Where: National Center, Visitor Center, Room 1C400

Website:; E-mail:


The USGS Science Strategy highlights the importance of understanding ecosystems and predicting global change due to climate and land use with long-term observational records. This core research objective is critically important in dryland regions of the western United States, which house the majority of land managed by the Department of Interior (DOI). These already water limited regions contain fragile ecosystems that have experienced, and will experience some of the largest increases in warming, drought, and human population growth in the country according to model projections. Accurate forecasts of climate and land use-induced changes in desert plant species assemblages are needed by managers because water-limited ecosystems are vulnerable to abrupt and potentially irreversible degradation and reductions in productivity, diversity, and ecosystem services.

Methods and Objectives

To better inform management responses to broad-scale global change impacts, Dr. Munson has synthesized over a century (1906-2012) of climate and vegetation observational records from DOI and other federally managed land at 25 sites (1500+ study plots) across the Colorado Plateau (cold desert), Sonoran, Chihuahuan, and Mojave Deserts (warm deserts). In collaboration with managers and scientists, he is using this growing network of sites, to answer the questions: 1) which plant species may be the most sensitive to climate change and what is the magnitude of their changes?, 2) how does the regional impact of climate on vegetation compare to land use impact?, 3) what are the ecosystem consequences, including soil erosion, wildlife habitat, and carbon storage of these climate and land-use induced vegetation changes?

Plant Responses

He will demonstrate both linear and nonlinear responses of key dominant plant species, plant diversity, and associated ecosystem processes to drought and elevated temperature across deserts. Cross-site and cross-desert comparisons reveal regional differences in how plants respond to climate and the importance of soil, landscape, and biotic characteristics in modifying climate-vegetation relationships in dryland ecosystems.  He will highlight “climate pivot points” that mark important shifts from increases to decreases in plant abundance along climatic gradients, and will show how land use can interact with climate-induced vegetation changes. These results are being used to assist with short-term management decisions, improve monitoring protocols, and inform climate change vulnerability assessments for DOI and federal land managers.

Representative Publications

Munson, S.M., R.H. Webb, J.A. Hubbard, J. Belnap, D.E. Swann, S. Rutman. 2012. Forecasting climate change impacts to plant community composition in the Sonoran Desert region. Global Change Biology 18: 1083-1095.

Munson, S.M., J. Belnap, G.S. Okin. 2011. Responses of wind erosion to climate-induced vegetation changes on the Colorado Plateau. Proceedings of the National Academy of Sciences 108: 3854-3859.

Munson, S.M., R.H. Webb, and J.A. Hubbard. 2011. A comparison of methods to assess long-term changes in  Sonoran Desert vegetation. Journal of Arid Environments 75: 1228-1231.

Munson, S.M., J. Belnap, C.D. Schelz, M. Moran, and T.W. Carolin. 2011. On the brink of change: plant responses to climate on the Colorado Plateau. Ecosphere 2: Article 68.

Seminar Contacts:

Dr. Rama K. Kotra,

Ms. Elizabeth Wasserman,