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Field guide to Mount Baker volcanic deposits in the Baker River valley: Nineteenth century lahars, tephras, debris avalanches, and early Holocene subaqueous lava
Abstract
Holocene volcanic deposits from Mount Baker are plentiful in the low-lying Baker River valley at the eastern foot of the volcano. Tephra set SC (8850 yr B.P.), erupted from the nearby Schreibers Meadow cinder cone, is sporadically present. Exposures of both subaerial and subaqueous facies of the associated Sulphur Creek basalt lava flow are easy to access; the lava, the most mafic product known from the entire Mount Baker volcanic field, entered Glacial Lake Baker, invaded lacustrine sediments, and formed peperites as well as subaqueous block-and-ash flows. A volcaniclastic delta was deposited in the lake above the lava. The peperite and delta can be seen in the walls of Sulphur Creek, and in the banks of Baker Lake when the reservoir is drawn down in winter and early spring.
The best exposures of volcaniclastic flank assemblages from Mount Baker are found in the Baker River valley. The Boulder Creek assemblage formed a thick fan between the end of the Vashon glaciation and the deposition of the SC tephra. Now deeply trenched by Boulder Creek, lahar and block-and-ash diamicts can be seen with some effort by ascending the creek 2 km. A tiny vestige is exposed along the Baker Lake Road.
Much younger deposits are also accessible. In 1843, tephra set YP, erupted from Sherman Crater, was deposited in the valley. In ca. 1845–1847, the Morovitz Creek lahar swept down Boulder, Park, Morovitz, and Swift Creeks and inundated much of the current location of the Baker Lake reservoir. This lahar is an example of the most likely future hazard at Mount Baker as well as the most common type of lahar produced during the Holocene at the volcano—clay-rich or cohesive lahars initiated as slope failures from hydrothermally altered rock. They commonly increase in volume by entraining sediment as they flow. When thermal emissions from Sherman Crater increased in 1975–1976, the level of the reservoir was lowered to accommodate inflow of lahars such as the Morovitz Creek lahar. Renewed activity at Sherman Crater will again trigger reservoir drawdown. In 1890–1891, and again ca. 1917–1932, debris avalanches from pre–Mount Baker lavas flowed down Rainbow Creek. The largest, which flowed 10.5 km, can be visited at the Rainbow Falls overlook. Here, the peak discharge of the flow, derived from reconstructed cross sections defined by well-exposed lateral levees and from reported velocities of equivalent modern flows, is estimated to have been greater than the peak discharge of any historic flood in the Mississippi River.
... d) Sherman Crater (John Scurlock, 2005); Layering of massive flows, generally unaltered, with generally altered brecciated layers (orange colors). as~7.5 m thick downstream, likely reaching Puget Sound (Scott, 2003;Tucker et al., 2007) (arrows, Fig. 1). Smaller debris avalanches, with volumes less than~0.5 × 10 6 m 3 and runouts b~3 km have originated from Sherman Peak (Tucker and Scott, 2006). ...
... The amount of water on a volcano, both contained in perched aquifers, as well as in ice, also influences whether debris avalanches transform into lahars (Delcamp et al., 2016;Scott, 2003;Scott et al., 2000;Scott et. al., 2001;Tucker et al., 2007;Vallance and Scott, 1997). The resistivity model (Fig. 7) images significant amounts of water that may continue throughout the volcano (dashed blue lines, Fig. 8), resulting in saturated and unsaturated zones as inferred for other volcanoes (Aizawa et al., 2009;Ball et al., 2018). ...
Water-saturated hydrothermal alteration reduces the strength of volcanic edifices, increasing the potential for catastrophic sector collapses that can lead to far traveled and destructive debris flows. Intense hydrothermal alteration significantly lowers the resistivity and magnetization of volcanic rock and therefore hydrothermally altered rocks can be identified with helicopter electromagnetic and magnetic measurements. Geophysical models constrained by rock properties and geologic mapping show that intensely altered rock is restricted to two small (500 m diameter), >250 m thick regions around Sherman Crater and Dorr Fumarole Field at Mount Baker, Washington. This distribution of alteration contrasts with much thicker and widespread alteration encompassing the summits of Mounts Adams and Rainier prior to the 5600 year old Osceola collapse, which is most likely due to extreme erosion and the limited duration of summit magmatism at Mount Baker. In addition, the models suggest that the upper ~300 m of rock contains water which could help to lubricate potential debris flows. Slope stability modeling incorporating the geophysically modeled distribution of alteration and water indicates that the most likely and largest (~0.1 km³) collapses are from the east side of Sherman Crater. Alteration at Dorr Fumarole Field raises the collapse hazard there, but not significantly because of its lower slope angles. Geochemistry and analogs from other volcanoes suggest a model for the edifice hydrothermal system.
... d) Sherman Crater (John Scurlock, 2005); Layering of massive flows, generally unaltered, with generally altered brecciated layers (orange colors). as~7.5 m thick downstream, likely reaching Puget Sound (Scott, 2003;Tucker et al., 2007) (arrows, Fig. 1). Smaller debris avalanches, with volumes less than~0.5 × 10 6 m 3 and runouts b~3 km have originated from Sherman Peak (Tucker and Scott, 2006). ...
... The amount of water on a volcano, both contained in perched aquifers, as well as in ice, also influences whether debris avalanches transform into lahars (Delcamp et al., 2016;Scott, 2003;Scott et al., 2000;Scott et. al., 2001;Tucker et al., 2007;Vallance and Scott, 1997). The resistivity model (Fig. 7) images significant amounts of water that may continue throughout the volcano (dashed blue lines, Fig. 8), resulting in saturated and unsaturated zones as inferred for other volcanoes (Aizawa et al., 2009;Ball et al., 2018). ...
High‐resolution helicopter magnetic and electromagnetic (HEM) data flown over the rugged, ice‐covered Mt. Adams, Mt. Baker and Mt. Rainier volcanoes (Washington), reveal the distribution of alteration, water and ice thickness essential to evaluating volcanic landslide hazards. These data, combined with geological mapping and rock property measurements, indicate the presence of appreciable thicknesses (>500 m) of water‐saturated hydrothermally altered rock west of the modern summit of Mount Rainier in the Sunset Amphitheater region and in the central core of Mount Adams north of the summit. Alteration at Mount Baker is restricted to thinner (<300 m) zones beneath Sherman Crater and the Dorr Fumarole Fields. The EM data identified water‐saturated rocks from the surface to the detection limit (100–200 m) in discreet zones at Mt. Rainier and Mt Adams and over the entire summit region at Mt. Baker. The best estimates for ice thickness are obtained over relatively low resistivity (<800 ohm‐m) ground for the main ice cap on Mt. Adams and over most of the summit of Mt. Baker. The modeled distribution of alteration, pore fluids and partial ice volumes on the volcanoes helps identify likely sources for future alteration‐related debris flows, including the Sunset Amphitheater region at Mt. Rainier, steep cliffs at the western edge of the central altered zone at Mount Adams and eastern flanks of Mt. Baker.
... But there was not simply one archetypal flood theme: many Pacific Northwest stories document local consequences of real-world events, notably the Cascadia subduction zone earthquake, tsunami, and landslides of 1700 CE (Budhwa , 2018McMillan and Hutchinson 2002;Ludwin et al. 2005). Accordingly, some claimed "borrowings" of flood stories could instead record the well-documented underlying commonalities of debris flow and outburst-flood dynamics from drainage to drainage, as evident in the pattern of upstream scouring (reaming) of riparian corridors, downstream deposition of gravelly sands, and creation of major log-jams affecting fisheries, all (for example) accompanying the 1980 eruption of Mount St. Helens (Major and Mark 2006) and 19th-Century activity of Mount Baker (Tucker et al. 2007). ...
Indigenous oral traditions of the Líl̓wat Nation recount observations of Qw̓elqw̓elústen (Mount Meager), a Garibaldi Volcanic Belt volcano in southwestern British Columbia, Canada; and associated eruptive activity, mass-wasting, and outburst flooding. We present Líl̓wat observations relating to Qw̓elqw̓elústen’s ∼2360 cal year B.P. eruption and its aftermath, a devastating outburst flood down the Lillooet valley. The Copper Canoe story correlates with the event sequence of pyroclastic damming of the Lillooet River and an outburst flood traveling far downstream, interrupting salmon runs and displacing people. Other stories suggest an eruptive plume and fumaroles. Recounted valley-floor changes, with proximal scouring and downstream filling of marshes allowing human resettlement, closely parallel and augment geological evidence, showing that oral traditions are equally important in holding landscape history. Oral traditions portray dramatic landscape changes, some by the Transformers, said to have traveled this land to make imperfect things right. Geologically documented debris-flow delta progradation and infill of the upper 50 km of Lillooet Lake since ∼12 000 cal B.P. underscore the land’s dynamism and the need for both sources to inform planning for future eruptive, mass-wasting, and flooding events. Traditional landscape knowledge, like Western science, is observational and evidence-based, though interpretations can differ given Indigenous belief in a sentient landscape, capable of acting with intention. Binding of stories to geographical locations has functioned as a powerful mnemonic device to preserve orally transmitted information across many generations.
The Puget Sound is a complex fjord-estuary system in Washington State that is connected to the Pacific Ocean by the Juan de Fuca Strait and surrounded by several large population centers. The watershed is enormous, covering nearly 43,000 square kilometers with thousands of rivers and streams. Geological forces, volcanos, Ice Ages, and changes in sea levels make the Sound a biologically dynamic and fascinating environment, as well as a productive ecosystem. Human activity has also influenced the Sound. Humans built several major cities, such as Seattle and Tacoma, have dramatically affected the Puget Sound. This book describes the natural history and evolution of Puget Sound over the last 100 million years through the present and into the future. Key Features Summarizes a complex geological, geographical, and ecological history Reviews how the Puget Sound has changed and will likely change in the future Examines the different roles of various drivers of the Sound's ecosystem function Includes the role of humans-both first people and modern populations. Explores Puget Sound as an example of general bay ecological and environmental issues
Before the arrival of the Spaniards in America, between the fourteenth and sixteenth centuries A.D., events and daily life were described through symbols in documents called codices. During the conquest, the Spaniards destroyed many of the codices because they were viewed as idolatrous. In Mexico and overseas there exist a number of codex that were artistically and consistently drawn by the Tlacuilo people who had strong knowledge in different disciplines, including natural processes, biodiversity, war, and social and religious problems. These codices contain five kinds of glyphs: numerals, calendrical, pictographic, ideographic and phonetic. One codex that contains an especially large amount of information about natural processes such as climate, volcanic eruptions, and major earthquakes, is the Telleriano Remensis. A careful analysis of this codex and related documents provides evidence for 12 earthquakes defined in space and time. Earthquakes were represented by two combined symbols: motion and earth. These symbols are not related to earthquakes themselves, but together, represent a seismic event, whose effects could be related to intensities of V in the ESI 2007 scale. The effects interpreted in the codex (tilted buildings, rolling stones, landslides, and human migration) suggest that earthquake strengths are very similar to those described in the 2007 ESI scale. The Mexicas, influenced by the Mayan culture, assigned a determined number of bars (tlalli) to each earthquake giving them a numerical representation and scale. This indicates that prehispanic cultures, such as the Aztec (Mexicas), Mixtec and Zapotec, already had some assessment criteria to scale earthquakes and their effects.
As the Vashon glacier retreated from its terminal position in the southern Puget-Lowland and thinned rapidly, marine waters invaded the central and northern lowland, floating the ice and depositing Everson glaciomarine drift over a wide area from southern Whidbey Island to southern British Columbia. The Everson deposits are characterized by vast areas of massive, poorly sorted stony silt and clay commonly containing marine shells. At Bellingham Bay and elsewhere in the Fraser Lowland, Deming sand is overlain by massive, poorly sorted, Bellingham glaciomarine drift to elevations of 180–210 m above present sea level and is underlain by Kulshan glaciomarine drift.
Following deposition of the Everson glaciomarine drift, ice readvanced into northern Washington and deposited Sumas Drift and meltwater channels were incised into the glaciomarine deposits. Four moraine-building phases are recognized in the Sumas, the last two in the Younger Dryas.
Rapid deglaciation between 14,500 and 12,500 ¹⁴C yr B.P. resulted in lowering of the surface the Cordilleran Ice Sheet below ridge crests in the Nooksack drainage and glacial activity thereafter became topographically controlled. Local valley glaciers in the upper Nooksack Valley were fed by alpine glaciers on Mount Baker, Mount Shuksan, and the Twin Sisters Range that were no longer connected to the Cordilleran Ice Sheet. Remnants of the Cordilleran Ice Sheet persisted in the Fraser Lowland at that time but were separated from the Nooksack Valley glaciers by several ridges 1200 m higher than the surface of the ice sheet. Alpine glaciers deposited drift in the Middle and North forks of the Nooksack drainage 25–45 km down-valley from their sources.
Large mega-landslides in the Nooksack drainage are associated with an area of unusually high seismic activity, whereas nearby areas having the same geology, topography, climate, and vegetation have no such mega-landslides, suggesting that the landslides are seismically induced.
Five Holocene tephras have been recognized in the region around Mount Baker–Schreibers Meadow scoria, Mazama ash, Rocky Creek ash, Cathedral Crag ash, and the 1843 tephra.
Mount Baker volcano displayed a short interval of seismically-quiescent thermal unrest in 1975, with high emissions of magmatic
gas that slowly waned during the following three decades. The area of snow-free ground in the active crater has not returned
to pre-unrest levels, and fumarole gas geochemistry shows a decreasing magmatic signature over that same interval. A relative
microgravity survey revealed a substantial gravity increase in the ~30years since the unrest, while deformation measurements
suggest slight deflation of the edifice between 1981–83 and 2006–07. The volcano remains seismically quiet with regard to
impulsive volcano-tectonic events, but experiences shallow (<3km) low-frequency events likely related to glacier activity,
as well as deep (>10km) long-period earthquakes. Reviewing the observations from the 1975 unrest in combination with geophysical
and geochemical data collected in the decades that followed, we infer that elevated gas and thermal emissions at Mount Baker
in 1975 resulted from magmatic activity beneath the volcano: either the emplacement of magma at mid-crustal levels, or opening
of a conduit to a deep existing source of magmatic volatiles. Decadal-timescale, multi-parameter observations were essential
to this assessment of magmatic activity.
KeywordsQuiescent degassing–Thermal unrest–Microgravity–Volcano deformation–Stalled intrusion–Cascade Range
The ca. 8800 14C yrs BP Sulphur Creek lava flowed eastward 12 km from the Schriebers Meadow cinder cone into the Baker River valley, on the southeast flank of Mount Baker volcano. The compositionally-zoned basaltic to basaltic andesite lava entered, crossed and partially filled the 2-km-wide and > 100-m-deep early Holocene remnant of Glacial Lake Baker. The valley is now submerged beneath a reservoir, but seasonal drawdown permits study of the distal entrant lava. As a lava volume that may have been as much as 180 × 106 m3 entered the lake, the flow invaded the lacustrine sequence and extended to the opposite (east) side of the drowned Baker River valley. The volume and mobility of the lava can be attributed to a high flux rate, a prolonged eruption, or both. Basalt exposed below the former level of the remnant glacial lake is glassy or microcrystalline and sparsely vesicular, with pervasive hackly or blocky fractures. Together with pseudopillow fractures, these features reflect fracturing normal to penetrative thermal fronts and quenching by water. A fine-grained hyaloclastite facies was probably formed during quench fragmentation or isolated magma-water explosions. Although the structures closely resemble those developed in lava-ice contact environments, establishing the depositional environment for lava exhibiting similar intense fracturing should be confirmed by geologic evidence rather than by internal structure alone. The lava also invaded the lacustrine sequence, forming varieties of peperite, including sills that are conformable within the invaded strata and resemble volcaniclastic breccias. The peperite is generally fragmental and clast- or matrix-supported; fine-grained and rounded fluidal margins occur locally. The lava formed a thickened subaqueous plug that, as the lake drained in the mid-Holocene, was exposed to erosion. The Baker River then cut a 52-m-deep gorge through the shattered, highly erodible basalt.
New radiocarbon dates associated with volcanic ashes and lahars improve our understanding of the volcanic activity of Mount Baker, a 3284 m-high, andesitic stratovolcano in the North Cascades, Washington. The geologic record shows that during the Holocene, four ashes and at least seven lahars were deposited on the flanks of Mount Baker and in the nearby North Cascades. Here, we document the ages of three previously undated ashes, the Schriebers Meadow scoria, the Rocky Creek ash, and the Cathedral Crag ash. Because Mount Baker lies at the head of the Nooksack drainage, eruptive activity may influence areas downstream. Understanding the timing and characteristics of volcanic eruptions from Mount Baker is useful from volcanic hazard and paleoclimatological perspectives.
As the Vashon glacier retreated from its terminal position in the southern Puget-Lowland and thinned rapidly, marine waters invaded the central and northern lowland, floating the ice and depositing Everson glaciomarine drift over a wide area from southern Whidbey Island to southern British Columbia. The Everson deposits are characterized by vast areas of massive, poorly sorted stony silt and clay commonly containing marine shells. At Bellingham Bay and elsewhere in the Fraser Lowland, Deming sand is overlain by massive, poorly sorted, Bellingham glaciomarine drift to elevations of 180–210 m above present sea level and is underlain by Kulshan glaciomarine drift.
Following deposition of the Everson glaciomarine drift, ice readvanced into northern Washington and deposited Sumas Drift and meltwater channels were incised into the glaciomarine deposits. Four moraine-building phases are recognized in the Sumas, the last two in the Younger Dryas.
Rapid deglaciation between 14,500 and 12,500 ¹⁴C yr B.P. resulted in lowering of the surface the Cordilleran Ice Sheet below ridge crests in the Nooksack drainage and glacial activity thereafter became topographically controlled. Local valley glaciers in the upper Nooksack Valley were fed by alpine glaciers on Mount Baker, Mount Shuksan, and the Twin Sisters Range that were no longer connected to the Cordilleran Ice Sheet. Remnants of the Cordilleran Ice Sheet persisted in the Fraser Lowland at that time but were separated from the Nooksack Valley glaciers by several ridges 1200 m higher than the surface of the ice sheet. Alpine glaciers deposited drift in the Middle and North forks of the Nooksack drainage 25–45 km down-valley from their sources.
Large mega-landslides in the Nooksack drainage are associated with an area of unusually high seismic activity, whereas nearby areas having the same geology, topography, climate, and vegetation have no such mega-landslides, suggesting that the landslides are seismically induced.
Five Holocene tephras have been recognized in the region around Mount Baker–Schreibers Meadow scoria, Mazama ash, Rocky Creek ash, Cathedral Crag ash, and the 1843 tephra.
Volcanic H2S emission rate data are scant despite their importance in understanding magma degassing. We present results from direct airborne plume measurements of H2S and CO2 on a 21-orbit survey at eleven different altitudes around Mount Baker volcano in September 2000 utilizing instrumentation mounted in a light aircraft. Measured emission rates of H2S and CO2 were 5.5 td−1 and 187 td−1 respectively. Maximum concentrations of H2S and CO2 encountered within the 4-km-wide plume were 75 ppb and 2 ppm respectively. Utilizing the H2S signal as a marker for the plume allows the corresponding CO2 signal to be more easily and accurately distinguished from ambient CO2 background. This technique is sensitive enough for monitoring weakly degassing volcanoes in a pre-eruptive condition when scrubbing by hydrothermal fluid or aquifers might mask the presence of more acid magmatic gases such as SO2.
Mount Baker, a steaming, ice-mantled, andesitic stratovolcano, is the most conspicuous component of a multivent Quaternary volcanic field active almost continuously since 1.3 Ma. More than 70 packages of lava flows and ∼110 dikes have been mapped, ∼500 samples chemically analyzed, and ∼80 K-Ar and 40Ar/39Ar ages determined. Principal components are (1) the ignimbrite-filled Kulshan caldera (1.15 Ma) and its precaldera and postcaldera rhyodacite lavas and dikes (1.29-0.99 Ma); (2) ∼60 intracaldera, hydrothermally altered, andesite-dacite dikes and pods-remnants of a substantial early-postcaldera volcanic center (1.1-0.6 Ma); (3) unaltered intracaldera andesite lavas and dikes, including those capping Ptarmigan and Lasiocarpa Ridges and Table Mountain (0.5-0.2 Ma); (4) the long-lived Chowder Ridge focus (1.29-0.1 Ma)-an andesite to rhyodacite eruptive complex now glacially reduced to ∼50 dikes and remnants of ∼10 lava flows; (5) Black Buttes stratocone, basaltic to dacitic, and several contemporaneous peripheral volcanoes (0.5-0.2 Ma); and (6) Mount Baker stratocone and contemporaneous peripheral volcanoes (0.1 Ma to Holocene). Glacial ice has influenced eruptions and amplified erosion throughout the lifetime of the volcanic field. Although more than half the material erupted has been eroded, liberal and conservative volume estimates for 77 increments of known age yield cumulative curves of volume erupted vs. time that indicate eruption rates in the range 0.17-0.43 km3/k.y. for major episodes and longterm background rates of 0.02-0.07 km3/k.y. Andesite and rhyodacite each make up nearly half of the 161 ± 56 km3 of products erupted, whereas basalt and dacite represent only a few cubic kilometers, each representing 1%-3% the total. During the past 4 m.y., the principal magmatic focus has migrated stepwise 25 km southwestward, from the edge of the Chilliwack batholith to present-day Mount Baker.
The Holocene Sulphur Creek basaltic andesite, which erupted from a small cinder cone on the southern flank of Mount Baker, locally contains 1–15 cm spheroidal to tongue-shaped inclusions of high-alumina basalt. Textural and chemical relationships indicate that the basalt was mixed with and quenched within the host lava, but that there was little or no homogenization of the two magmas. Both Sulphur Creek liquids had temperatures in excess of 1000°C, and mixing probably occurred at temperatures less than 1150°C at a pressure betweeen 0.5 and 2.0 kbar. Available evidence suggests that mixing of the two magmas did not result from simultaneous flow within the Sulphur Creek conduit, but rather occurred within a density-stratified magma chamber. The initial density contrast between basaltic and basaltic andesite liquids was determined by the thermal and compositional contrast across their interface, and the oxidation state, water content, and crystallinity of the two magma columns. The bulk density of the basalt was probably only slightly greater than that of basaltic andesite due to the high crystal content of the more-differentiated liquid. The basalt would not have had to reach water-saturation in order for the densities of the two liquids to become equal. Overturning of the magma chamber could have occurred without the requirement of volatile exsolution in the lower mafic layer.
Measurements of H and V (dimensions in the horizontal and vertical directions of pillows exposed in vertical cross-section) were made on 19 pillow lavas from the Azores, Cyprus, Iceland, New Zealand, Tasmania, the western USA and Wales. The median values of H and V plot on a straight line that defines a spectrum of pillow sizes, having linear dimensions five times greater at one end than at the other, basaltic toward the small-size end and andesitic toward the large-size end. The pillow median size is interpreted to reflect a control exercised by lava viscosity. Pillows erupted on a steep flow-foot slope in lava deltas can, however, have a significantly smaller size than pillows in tabular pillowed flows (inferred to have been erupted on a small depositonal slope), indicating that the slope angle also exercised a control. Pipe vesicles, generally abundant in the tabular pillowed flows and absent from the flow-foot pillows, have potential as a paleoslope indicator. Pillows toward the small-size end of the spectrum are smooth-surfaced and grew mainly by stretching of their skin, whereas disruption of the skin and spreading were important toward the large-size end. Disruption involved increasing skin thicknesses with increasing pillow size, and pillows toward the large-size end are more analogous with toothpaste lava than with pahoehoe and are inferred from their thick multiple selvages to have taken hours to grow. Pseudo-pillow structure is also locally developed. An example of endogenous pillow-lava growth, that formed intrusive pillows between normal pillows, is described from Sicily. Isolated pillow-like bodies in certain andesitic breccias described from Iceland were previously interpreted to be pillows but have anomalously small sizes for their compositions; it is now proposed that they may lack an essential attribute of pillows, namely, the development of bulbous forms by the inflation of a chilled skin, and are hence not true pillows. Para-pillow lava is a common lava type in the flow-foot breccias. It forms irregular flow-sheets that are locally less than 5 cm thick, and failed to be inflated to pillows perhaps because of an inadequate lava-supply rate or too high a flow velocity.