of processes on regional and local scales was spotty at best. However, the
ongoing “digital revolution” has significantly improved the observational
capabilities of Earth science through the development of many new
remotesensing and direct-sampling technologies. In addition, data-gathering
efforts have been greatly facilitated by worldwide communication systems that
can transmit high-resolution observations of many variables from remote
locations in real or near-real time. Newly available technologies range from
space-based platforms and global networks of surface observatories to extremely
sensitive instruments that can measure Earth materials and processes in both the
laboratory and the field.
Laser altimetry from aircraft can be combined with accurate digital elevation
models to investigate the surficial processes of erosion and sedimentation at the
meter scale. Interferometric synthetic aperture radar aboard satellites can map
decimeter-level deformations of fault ruptures, magma inflation of volcanoes, and
ground subsidence continuously over areas tens to hundreds of kilometers wide.
These images of the strain field complement the even more precise, pointwise
measurements from the satellite-based Global Positioning System (GPS). GPS
receivers can be located with millimeter precision over baselines of thousands of
kilometers and can thus be used to map long-term strain rates across wide plate
boundaries, such as in the western United States, while arrays of GPS stations can
be used to measure the short-term deformations associated with volcanoes and
earthquakes.
Observing processes that are active beneath the solid surface is particularly
challenging, because the Earth’s interior is inaccessible and characterized by
extreme conditions. Rocks in the outer few kilometers of the crust can be sampled
directly by trenching, tunneling, and drilling. Trenching to a depth of a few
meters provides a means of studying environments (e.g., paleosols, fluvial
systems) and processes (e.g., weathering, faulting) that operated in the relatively
recent geological past. Paleoseismologists have made particularly effective use of
trenching techniques to discover and date precisely the history of individual large
earthquakes on major faults. Although laborious and expensive, drilling is often
the best method for probing more deeply buried rock masses and collecting in situ
measurements of active geological processes. Novel logging techniques
developed by the petroleum industry, such as nuclear magnetic resonance and
electromagnetic borehole imaging, are furnishing unparalleled data on the
environments deep within sedimentary basins and continental basement rocks.
The German KTB drilling project, which penetrated to a depth of 9100 m in
1994, furnished key insights into crustal processes, revealing the near-critical
state of crustal stress predicted by Byerly’s relationship, which has important
implications for earthquake mechanics. In addition, the project confirmed
hydrostatic pore pressure at great depth in the Earth’s crust and detailed
geochemical data provided
BASIC EARTH SCIENCE AND SOCIETY
29
About this PDF file: This new digital representation of the
original work has been recomposed from XML files created
from the original paper book, not from the original
typesetting files. Page breaks are true to the original; line lengths,
word breaks, heading styles, and other typesetting-specific
formatting, however, cannot be retained,
and some typographic errors may have been accidentally inserted.
Please use the print version of this publication as the authoritative
version for attribution.
ongoing “digital revolution” has significantly improved the observational
capabilities of Earth science through the development of many new
remotesensing and direct-sampling technologies. In addition, data-gathering
efforts have been greatly facilitated by worldwide communication systems that
can transmit high-resolution observations of many variables from remote
locations in real or near-real time. Newly available technologies range from
space-based platforms and global networks of surface observatories to extremely
sensitive instruments that can measure Earth materials and processes in both the
laboratory and the field.
Laser altimetry from aircraft can be combined with accurate digital elevation
models to investigate the surficial processes of erosion and sedimentation at the
meter scale. Interferometric synthetic aperture radar aboard satellites can map
decimeter-level deformations of fault ruptures, magma inflation of volcanoes, and
ground subsidence continuously over areas tens to hundreds of kilometers wide.
These images of the strain field complement the even more precise, pointwise
measurements from the satellite-based Global Positioning System (GPS). GPS
receivers can be located with millimeter precision over baselines of thousands of
kilometers and can thus be used to map long-term strain rates across wide plate
boundaries, such as in the western United States, while arrays of GPS stations can
be used to measure the short-term deformations associated with volcanoes and
earthquakes.
Observing processes that are active beneath the solid surface is particularly
challenging, because the Earth’s interior is inaccessible and characterized by
extreme conditions. Rocks in the outer few kilometers of the crust can be sampled
directly by trenching, tunneling, and drilling. Trenching to a depth of a few
meters provides a means of studying environments (e.g., paleosols, fluvial
systems) and processes (e.g., weathering, faulting) that operated in the relatively
recent geological past. Paleoseismologists have made particularly effective use of
trenching techniques to discover and date precisely the history of individual large
earthquakes on major faults. Although laborious and expensive, drilling is often
the best method for probing more deeply buried rock masses and collecting in situ
measurements of active geological processes. Novel logging techniques
developed by the petroleum industry, such as nuclear magnetic resonance and
electromagnetic borehole imaging, are furnishing unparalleled data on the
environments deep within sedimentary basins and continental basement rocks.
The German KTB drilling project, which penetrated to a depth of 9100 m in
1994, furnished key insights into crustal processes, revealing the near-critical
state of crustal stress predicted by Byerly’s relationship, which has important
implications for earthquake mechanics. In addition, the project confirmed
hydrostatic pore pressure at great depth in the Earth’s crust and detailed
geochemical data provided
BASIC EARTH SCIENCE AND SOCIETY
29
About this PDF file: This new digital representation of the
original work has been recomposed from XML files created
from the original paper book, not from the original
typesetting files. Page breaks are true to the original; line lengths,
word breaks, heading styles, and other typesetting-specific
formatting, however, cannot be retained,
and some typographic errors may have been accidentally inserted.
Please use the print version of this publication as the authoritative
version for attribution.