Geology topics

Patrick T. Pringle

Publications and source records attributed to Patrick T. Pringle.

7 recordsLinked to original sources

USGS2023

A multifault earthquake threat for the Seattle metropolitan region revealed by mass tree mortality

Compound earthquakes involving simultaneous ruptures along multiple faults often define a region’s upper threshold of maximum magnitude. Yet, the potential for linked faulting remains poorly understood given the infrequency of these events in the historic era. Geological records provide longer perspectives, although temporal uncertainties are too broad to clearly pinpoint single multifault events. Here, we use dendrochronological dating and a cosmogenic radiation pulse to constrain the death dates of earthquake-killed trees along two adjacent fault zones near Seattle, Washington to within a 6-month period between the 923 and 924 CE growing seasons. Our narrow constraints conclusively show linked rupturing that occurred either as a single composite earthquake of estimated magnitude 7.8 or as a closely spaced double earthquake sequence with estimated magnitudes of 7.5 and 7.3. These scenarios, which are not recognized in current hazard models, increase the maximum earthquake size needed for seismic preparedness and engineering design within the Puget Sound region of >4 million residents.

Washington↗

USGS2022

Age of the late Holocene Bonneville landslide and submerged forest of the Columbia River Gorge, Oregon and Washington, USA, by radiocarbon dating

The late Holocene Bonneville landslide, a 15.5 km 2 rockslide-debris avalanche, descended 1000 m from the north side of the Columbia River Gorge and dammed the Columbia River where it bisects the Cascade Range of Oregon and Washington, USA. The landslide, inundation, and overtopping created persistent geomorphic, ecologic, and cultural consequences to the river corridor, reported by Indigenous narratives and explorer accounts, as well as scientists and engineers. From new dendrochronology and radiocarbon dating of three trees killed by the landslide, one entrained and buried by the landslide and two killed by rising water in the impounded Columbia River upstream of the blockage, we find (1) the two drowned trees and the buried tree died the same year, and (2) the age of tree death, and hence the landslide (determined by combined results of nine radiocarbon analyses of samples from the three trees), falls within AD 1421–1455 (3σ confidence interval). This result provides temporal context for the tremendous physical, ecological, and cultural effects of the landslide, as well as possible triggering mechanisms. The age precludes the last Cascadia Subduction Zone earthquake of AD 1700 as a landslide trigger, but not earlier subduction zone or local crustal earthquakes.

Oregon, Washington↗

USGS2010

Magnitude and timing of downstream channel aggradation and degradation in response to a dome-building eruption at Mount Hood, Oregon

A dome-building eruption at Mount Hood, Oregon, starting in A.D. 1781 and lasting until ca. 1793, produced dome-collapse lithic pyroclastic flows that triggered lahars and intermittently fed 10 8 m 3 of coarse volcaniclastic sediment to sediment reservoirs in headwater canyons of the Sandy River. Mobilization of dominantly sandy sediment from these reservoirs by lahars and seasonal floods initiated downstream migration of a sediment wave that resulted in a profound cycle of aggradation and degradation in the lowermost reach of the river (depositional reach), 61-87 km from the source. Stratigraphic and sedimentologic relations in the alluvial fill, together with dendrochronologic dating of degradation terraces, demonstrate that (1) channel aggradation in response to sediment loading in the headwater canyons raised the river bed in this reach at least 23 m in a decade or less; (2) the transition from aggradation to degradation in the upper part of this reach roughly coincided with the end of the dome-building eruption; (3) fluvial sediment transport and deposition, augmented by one lahar, achieved a minimum average aggradation rate of ~2 m/yr; (4) the degradation phase of the cycle was more prolonged than the aggradation phase, requiring more than half a century for the river to reach its present bed elevation; and (5) the present longitudinal profile of the Sandy River in this reach is at least 3 m above the pre-eruption profile. The pattern and rate of channel response and recovery in the Sandy River following heavy sediment loading resemble those of other rivers similarly subjected to very large sediment inputs. The magnitude of channel aggradation in the lower Sandy River, greater than that achieved at other volcanoes following much larger eruptions, was likely enhanced by lateral confinement of the channel within a narrow incised valley. A combination of at least one lahar and winter floods from frequent moderate-magnitude rainstorms and infrequent very large storms was responsible for flushing large volumes of sediment to the depositional reach. These conditions permitted a sedimentation response in the Sandy River that approached the magnitude of channel aggradation resulting elsewhere from large explosive eruptions and high-intensity rainfall regimes, despite the fact that the Sandy River aggradation was in response to an unremarkable dome-building eruption in a climate dominated by low to moderate rainfall intensities.

Oregon↗

USGS2010

Late eighteenth century Old Maid eruption and lahars at Mount Hood, Oregon (USA) dated with tree rings and historical observations

Tree rings of subfossil trees buried by lahars and lahar-derived sediments along the Sandy and Zigzag Rivers record the onset of a late eighteenth century eruption at Mount Hood, Oregon, USA (Figs. 1–2). Crandell (1980) described and named this eruptive activity the ‘Old Maid eruptive period’ and estimated its age at about “200–300 year” using radiocarbon ages of trees killed by lahars. Cameron and Pringle (1986, 1987, 1991) used dendrochronology to constrain the major eruptive events to several decades in the late 1700s. Precise dating of the Old Maid eruption using tree rings, however, has been complicated by the inconsistent wood quality and scarcity of victim subfossil trees. A lack of nearby master chronologies, diverse physiography and microclimates of the region, and the generally low sensitreivity of local tree-ring series to climate variation also create problems with interpretation.

Oregon↗

USGS2009

Eruption-related lahars and sedimentation response downstream of Mount Hood: Field guide to volcaniclastic deposits along the Sandy River, Oregon

Late Holocene dome-building eruptions at Mount Hood during the Timberline and Old Maid eruptive periods resulted in numerous dome-collapse pyroclastic flows and lahars that moved large volumes of volcaniclastic sediment into temporary storage in headwater canyons of the Sandy River. During each eruptive period, accelerated sediment loading to the river through erosion and remobilization of volcanic fragmental debris resulted in very high sediment-transport rates in the Sandy River during rain- and snowmelt-induced floods. Large sediment loads in excess of the river's transport capacity led to channel aggradation, channel widening, and change to a braided channel form in the lowermost reach of the river, between 61 and 87 km downstream from the volcano. The post-eruption sediment load moved as a broad bed-material wave, which in the case of the Old Maid eruption took ~2 decades to crest 83 km downstream. Maximum post-eruption aggradation levels of at least 28 and 23 m were achieved in response to Timberline and Old Maid eruptions. In each case, downstream aggradation cycles were initiated by lahars, but the bulk of the aggradation was achieved by fluvial sediment transport and deposition. When the high rates of sediment supply began to diminish, the river degraded, incising the channel fills and forming progressively lower sets of degradational terraces. A variety of debris-flow, hyperconcentrated-flow, and fluvial (upper and lower flow regime) deposits record the downstream passage of the sediment waves that were initiated by these eruptions. The deposits also presage a hazard that may be faced by communities along the Sandy River when volcanic activity at Mount Hood resumes.

Oregon↗

USGS1992

Sedimentology, behavior, and hazards of debris flows at Mount Rainier, Washington

Mount Rainier is potentially the most dangerous volcano in the Cascade Range because of its great height, frequent earthquakes, active hydrothermal system, and extensive glacier mantle. Many debris flows and their distal phases have inundated areas far from the volcano during postglacial time. Two types of debris flows, cohesive and noncohesive, have radically different behavior that relates empirically to clay content. The two types represent the observable end members of a continuum of debris flow characteristics at Mount Rainier. Cohesive flows exhibit behavior affected by the cohesion and adhesion of particles; noncohesive flows are dominated by particle collisions to the extent of extensive particle cataclasis during near-boundary shear. Cohesive debris flows contain more than 3 to 5 percent of clay-size sediment. The composition of these flows changed little during flow for more than 100 kilometers from Mount Rainier where they inundate parts of the now-populated Puget Sound Lowland. They originate as deep-seated failures of sectors of the volcanic edifice at a frequency indicating that such failures are the major destructional process of its morphologic evolution. In several deposits of large cohesive flows, a lateral, megaclast-bearing facies (with a mounded or hummocky surface) contrasts with a more clay-rich facies in the center of valleys and downstream. Cohesive flows at Mount Rainier do not correlate strongly with volcanic activity and thus can recur without warning, possibly triggered by nonmagmatic seismicity or by destabilization associated with the hydrothermal system. Noncohesive debris flows contain less than 3 to 5 percent of clay-size sediment. They form most commonly by hulking of sediment in water surges, but some originate directly or indirectly from shallow slope failures that do not penetrate the hydrothermally altered core of the volcano. In contrast with cohesive flows, most noncohesive flows transform both from and to other flow types, so that the debris flows are the middle segments of flow waves beginning and ending as flood surges. Proximally, through the bulking of poorly sorted, volcaniclastic debris on the flanks of the volcano, flow waves expand rapidly in volume by transforming from water surges through hyperconcentrated streamflow (20 to 60 percent sediment by volume) to debris flow. Distally, the transformations occur more slowly in reverse order--from debris flow, to hyperconcentrated flow, and finally to normal streamflow with less than 20 percent sediment by volume. During runout of the largest noncohesive flows, hyperconcentrated flow has occurred for as much as 40 to 70 kilometers. Lahars (volcanic debris flows and their deposits) occurred at Mount Rainier throughout later postglacial time and not as groups of closely time-related flows during discrete eruptive periods as at Mount St. Helens. An exception is a period of large noncohesive flows during and after construction of the modern summit cone. Laharrunout flows, the hyperconcentrated flows forming the distal phases of lahars, document the frequency and extent of noncohesive lahars. Deposits record the following transformations of debris flows: (1) the direct, progressive dilution of debris flow to hyperconcentrated flow, (2) deposition of successively finer grained lobes of debris until only the hyperconcentrated tail of the flow remains to continue downstream, and (3) dewatering of coarse debris flow deposits to yield fine-grained debris flow or hyperconcentrated flow. Three planning or design case histories represent different lengths of postglacial time. Case I is representative of large, infrequent (500 to 1,000 years on average) cohesive debris flows. These flows need to be considered in long-term planning in valleys around the volcano. Case II generalizes the noncohesive debris flows of intermediate size and recurrence (100 to 500 years). This case is appropriate for consideration in some structural design. Case III flows are relatively small but more frequent (less than 100 years on average).

Washington↗

USGS1989

Debris flows from tributaries of the Colorado River, Grand Canyon National Park, Arizona

A reconnaissance of 36 tributaries of the Colorado River indicates that debris flows are a major process by which sediment is transported to the Colorado River in Grand Canyon National Park. Debris flows are slurries of sediment and water that have a water content of less than about 40 percent by volume. Debris flows occur frequently in arid and semiarid regions. Slope failures commonly trigger debris flows, which can originate from any rock formation in the Grand Canyon. The largest and most frequent flows originate from the Permian Hermit Shale, the underlying Esplanade Sandstone of the Supai Group, and other formations of the Permian and Pennsylvanian Supai Group. Debris flows also occur in the Cambrian Muav Limestone and underlying Bright Angel Shale and the Quaternary basalts in the western Grand Canyon. Debris-flow frequency and magnitude were studied in detail in the Lava-Chuar Creek drainage at Colorado River mile 65.5; in the Monument Creek drainage at mile 93.5; and in the Crystal Creek drainage at mile 98.2. Debris flows have reached the Colorado River on an average of once every 20 to 30 years in the Lava-Chuar Creek drainage since about 1916. Two debris flows have reached the Colorado River in the last 25 years in Monument Creek. The Crystal Creek drainage has had an average of one debris flow reaching the Colorado River every 50 years, although the debris flow of 1966 has been the only flow that reached the Colorado River since 1900. Debris flows may actually reach the Colorado River more frequently in these drainages because evidence for all debris flows may not have been preserved in the channel-margin stratigraphy. Discharges were estimated for the peak flow of three debris flows that reached the Colorado River. The debris flow of 1966 in the Lava-Chuar Creek drainage had an estimated discharge of 4,000 cubic feet per second. The debris flow of 1984 in the Monument Creek drainage had a discharge estimated between 3,600 and 4,200 cubic feet per second. The debris flow of 1966 in the Crystal Creek drainage had a discharge estimated between 9,200 and 14,000 cubic feet per second. Determination of the effective cross-sectional area was a problem in all calculations involving superelevations on bends because areas near superelevation marks were 1.5 to 3.5 times larger than areas of upstream or downstream cross sections. Debris flows in the Grand Canyon generally are composed of 10 to 40 percent sand by weight and may represent a significant source of beach-building sand along the Colorado River. The particle-size distributions are very poorly sorted and the largest transported boulders were in the Crystal Creek drainage. The large boulders transported into the Colorado River by debris flows create or change hydraulic controls (rapids); these controls appear to be governed by the magnitude and frequency of tributary-flow events and the history of discharges on the Colorado River. Reworking of debris fans by the Colorado River creates debris bars that constrain the size of eddy systems and forms secondary rapids and riffles below tributary mouths.

Professional Paper↗