Geosciences in an Underground Laboratory: EarthLab

1. Geosciences in an Underground Laboratory: EarthLab W. M. Roggenthen SD School of Mines & Technology

2. EarthLab: A Subterranean Laboratory and Observatory to Study Microbial Life, Fluid Flow, and Rock Deformation Brian McPherson, New Mexico Institute of Mining and Technology Derek Elsworth, Pennsylvania State University Charles Fairhurst, University of Minnesota Stephen Kesler, University of Michigan Tullis Onstott, Princeton University William Roggenthen, SDSMT Herb Wang, University of Wisconsin http://www.earthlab.org

3. Requirements – what Geosciences need: 1. A large (~20+ km3) volume of rock with interesting geology. 2. Drill holes and underground workings in rocks reaching temperatures of 120°C - water-filled fracture systems. 3. Ability to introduce materials into holes, workings, or fractures to modify the geochemistry of the rock. 4. Existing geologic data and samples.

4. Homestake Mine, Lead, SD

5. EarthLab: • A “window” into the basement of North America

6. Microbial Life at Depth • Hydrologic Cycle • Rock-Water Chemistry • Rock Deformation and Fluid Flow • Deep Seismic Observatory

7. Microbial Life at Depth

8. The Ultradeep Life and BiogeochemistryObservatory • Purpose: • to search for the limits of life • what is living at depth? • how does it take advantage of its environment? • what is its metabolic rate/how does it grow?

9. Methods: • use closely spaced boreholes that: • attain depths up to 5 km • have bottom-hole temperatures of 110-120°C, the maximum known temperature for life

10. Homestake Mine, Lead, SD ~16,000 ft

11. Hydrologic Cycle

12. The Deep Flow and Paleoclimate Laboratory and Observatory Purpose: to search for continental paleoclimate records and document deep transport processes Methods: instrument a fracture zone extending from the surface to the maximum depth of the laboratory.

13. Deep Flow Hydrologic Experiments will provide information on the movement of groundwater in the crust and its relationship to Earth’s changing climate.

14. The Induced Fracture and Deformation Processes Laboratory Purpose: to conduct extensive studies of three-dimensional rock deformation in heterogeneous rock formations

15. Methods: • Instruments in boreholes will measure: • Rock deformation associated with mining out a large cavity • Creation of fractures using high-pressure fluid • Deformation resulting from heating small volumes of rock

16. Induced Fracture and Deformation Data are critical to scaling-up models used to predict long-term stability of subsurface excavations.

17. The Deep Seismic Observatory • Purpose: • To make the largest and best seismometer in the world. • Method: • The laboratory will become the instrument. • Will use a fully three-dimensional array consisting of at least 60 broadband seismometers in tunnels and boreholes.

18. Key Numbers for EarthLab Anticipated total tunnel length: ~ 10 km Greatest tunnel depth: ~ 2 - 2.5 km number of instrumented boreholes: ~ 140 total length of rock core to collect: ~ 15,000 m

19. Genetic materials - novel microorganisms • Analytical techniques for geomicrobiology • Environmental remediation • Subsurface imaging • Natural resource recovery