EarthLab would be a permanent facility. Much in the way they use the research
vessels of the Ocean Drilling Program to take turns accessing the ocean, scientists
could spend weeks to months watching Earth processes below the surface. The
facility could not only be used for specific experiments but also could provide
a longer-term platform for instrumentation such as three-dimensional seismic
As earth scientists, we find the opportunity to share the proposed facility simply invaluable. For example, the typical hydrogeologist or sedimentary basin geologist works with borehole data. A popular analogy for borehole data is to imagine drilling a hole into a wall to see the inside of the wall, but the hole is only one-eighth of an inch thick and the diameter of a thin thread. The snapshot of the wall that can be made within that hole is about the relative size of the snapshot gained by one borehole within a basin. One would have to determine the type and amount of wiring and other properties within the entire wall using a few of these tiny holes.
If you could knock a hole in the wall with a hammer, you might have a better chance. EarthLab is analogous to such a hole, the proposed facility being kilometers deep and kilometers wide. Imagine being within Earth itself, with tens of kilometers of volume accessible, able to monitor directly where water, gas and bacteria flow and why. To realize this goal, it is essential for hydrogeologists to go underground.
Fluid flow and transport: EarthLab would revolutionize the field of hydrogeology by providing in situ temporal and spatial measurements of fluid flow and transport over vast volumes and at great depths. It would provide the opportunity to verify and confirm through direct observations the fundamental physics and chemistry of fluid flow at depth, to this day only understood in the simplest of terms. Geophysical imaging techniques used to monitor this fluid flow will both assist the direct observations and be improved during the process. Knowledge of fluid flow and transport is important for assessing drinking and irrigation water supplies, hazardous waste disposal sites and remediation of contaminated groundwater.
It is well known that fluid flow and transport are active at great depths in the subsurface. However, the nature of that flow, its range of rates, and the role deep flow and transport play in other processes are largely unknown because they are extremely difficult to measure. Direct observations and experiments in the subsurface are rare, and Earths surface and boreholes are typically the only venues available for study. Unfortunately, samples of deep rocks obtained from drill holes are usually small and have been disturbed a great deal by the drilling process, making them poor materials for testing factors that control fluid flow.
Hydrology research is currently going on at the proposed nuclear waste repository at Yucca Mountain in Nevada. This underground facility, however, is much shallower than what is proposed for EarthLab.
Using tracer and geophysical imaging tests over the entire volume of the laboratory, EarthLab scientists would characterize rock structure, fracture connectivity and transport properties, and their variability with scale, with depth and with distance across the excavated zone. The ability to investigate the rock package directly after imaging or performing tracer tests may provide tremendous improvements in the techniques that can be applied in other investigations, such as those by the oil and gas industry and geothermal industry.
Life at depth: Geomicrobiologists
could use EarthLab to develop and test technologies for detecting life underground,
a potentially useful tool for exploring other planets. The discovery in the
past decade of what appears to be a subsurface biosphere has opened a new scientific
frontier. Earth sciences, chemistry, physics and biology are now merging to
provide insights into how microbial life on this planet, and possibly others,
may have originated and evolved and how subsurface microorganisms dissolve and
precipitate minerals, leaving behind trace fossils.
Imagine an artificial drilling mole, a tube filled with scientific instruments attached to a cable that could burrow hundreds of meters under the Martian landscape, searching for water, organic chemicals and indications of life. It will be impossible to develop such technologies without going underground to watch and test them directly.
EarthLab would advance our understanding of the origins, diversity, distribution, function and adaptation of microbial communities in deep, largely inaccessible, often extreme subsurface environments. This expansion of knowledge can only occur if the coupling between biological processes and those associated with heat, energy and fluid transport and rock deformation can be determined experimentally in situ.
One plan is to use EarthLab to evaluate what factors enable microbial communities to survive at great depths. A subsurface lab can make it easer to identify what minerals serve as nutrients and the ranges of physical conditions that enable growth.
Inside Stripa: During the 1970s, researchers with the Lawrence Berkeley National Laboratory used the abandoned Stripa iron mine in Stripa, Sweden, to investigate options for storing nuclear waste. They soon realized an underground laboratory would be valuable for earth scientists. From the Ernest Orlando Lawrence Berkeley National Laboratory image library.
In fact, the high sensitivity equipment used by the physicists to quantify low energy particle fluxes could also be used to measure the glacially slow pace of subsurface microbial life. Indeed, microbial life is probably one of the most complex processes to be studied at EarthLab requiring carefully planned, multidisciplinary interactions. For example, fluid velocities and diffusion control the flux of soluble nutrients to the microorganisms, and this flux is also controlled by the permeability and porosity of the rocks that host the microorganisms. In turn, microorganisms may precipitate minerals or generate gases that alter permeability and fluid flow. Fluid advection perturbs or controls microbial migration rates and influences temperatures. Typically, temperatures change slowly, but if the change is more rapid than the ability of the microorganisms to migrate, they must adapt or die. Fluid flow determines whether and where subsurface communities survive.
EarthLab would be the only facility in the world where these geomicrobiological and biogeochemical processes could be delineated as a function of temperature and pressure to depths of several kilometers.
Rock deformation: Knowledge
of rock strain, or deformation, is particularly important in evaluating earthquake
hazards. EarthLab would permit continuous, direct measurements of strain, and
provide an opportunity to evaluate factors that control it.
Rock strain and earth stresses deep in the subsurface are not well characterized, except for a limited number of measurements in deep boreholes and deep mines. Active rock strain can only be estimated by surface-based methods such as satellite-generated Interferometric Synthetic Aperture Radar and Global Positioning System data and associated analysis. As with permeability, how rock strain and stress vary as a function of position and sample volume, or measurement scale, are not well understood because sufficiently large volumes of rock at depth have not been adequately measured or characterized yet.
Access to the large rock volume in EarthLab would permit testing the hypothesis that Earths crust is critically stressed, that some portion of the rock is always close to failure by fracture. Repeated shearing of such fractures can keep flow paths open that might otherwise close by mineral cementation. The most significant rock permeability at depth, therefore, occurs in areas of critically stressed fractures. Mapping fractures, stress and fluid flow within the subsurface will help earth scientists to confirm or extend theories about the mechanics of earth deformations. Finally, active experiments, such as emplacing a heater in the rock mass, can improve our understanding of how coupled mechanical, chemical, and fluid flow properties respond to environmental changes.
Mineral resources and environmental
geochemistry: EarthLab will allow more complete direct testing of
mineral-forming hydrothermal processes that operate in the upper crust and that
form ore deposits. These processes have only been inferred from theory and from
observations of minerals after theyve formed. In other words, by studying
minerals in situ, in an actively evolving system, it will be possible
to verify directly what typically is inferred by indirect methods.
Specifically, many of the mineral resources on which society depends are formed or concentrated by fluid flow in the subsurface. These concentrations reflect both chemical and physical processes of the surrounding rock. Oil, natural gas and some brines are localized in the crust largely by their physical response to fluid flow. Most metals, such as iron, copper and gold, are localized by chemical processes involving dissolution and subsequent deposition of minerals containing these metals. In both cases, the fluid flow system that concentrates the mineral resource gathers material from a large volume of rock and concentrates it in much smaller volumes that we call mineral deposits. Studies in a deep laboratory would contribute to our understanding of mineral deposit formation both through more detailed study of ancient deposits, which are likely to be exposed in any deep lab, and through active experiments involving fluid flow under controlled conditions. Although considerable progress has been made in understanding the processes that form mineral deposits by observation of fossil systems, we badly need to study these processes in an active environment. In most cases, these active environments, such as geothermal areas, are too hot and deep for direct study.
Fluid flow through rocks is also critically important to the release and concentration of metals and organic compounds that are of environmental concern. Most such releases take place because, through the mining process, rock from deep in the crust is exposed to water and oxygen, causing minerals formed at depth to decompose. The most widely known of these processes is acid mine drainage, which results when pyrite is oxidized by near-surface waters. Most studies of acid mine drainage and related processes have been confined to the points at which these waters exit mines or other underground sources. EarthLab would allow more direct observations of the early stages of these processes at depth, which will lead to better methods to control or stop dispersal of elements and compounds.
The current set of data earth scientists use to model active or ancient hydrothermal or fluid and mineral processes is woefully inadequate to accurately model real systems. EarthLab would provide a unique experimental venue whereby laboratory measurements of these parameters can be directly validated. For the first time, geochemists will be able to calibrate directly the accuracy of their experimental extrapolations.
From remote to direct
Direct access for the study of deep subsurface processes is limited to the
few deep mines in the world and the small number of deep boreholes that penetrate
the crystalline basement. Work in deep mines is difficult because mines are
primarily industrial operations and because accessing areas of most interest
often constitutes serious engineering challenges.
Work with deep core samples is complicated by the small sample sizes and disturbance caused by drilling, and because it is often difficult to extend interpretations beyond the immediate vicinity of the borehole. Examining larger-scale subsurface processes is currently accomplished using methods such as measurements of seismic velocities and attenuation, satellite-based remote sensing, and gravity, magnetic and electrical methods. These techniques are used to infer Earths structure and processes, but all of them may be considered types of remote sensing. EarthLab would provide an opportunity to go well beyond point sampling and to verify remote sensing methods with direct observation and measurement.
Much as surgery permits a physician to examine internal bones and organs recognized on X-rays or CAT scans, EarthLab would be a fully instrumented, dedicated laboratory and observatory for scientists to examine Earths active interior.
will the lab be built?
Since the Homestake gold mine in Lead, S.D., closed in December of 2001,
physicists have been working for the mines conversion an underground
Other sites that have been suggested are:
A currently undeveloped site beneath Mount
San Jacinto near Palm Springs, Calif.
The Waste Isolation Pilot Plant (WIPP) near
The Soudan mine in Soudan, Minn.