Ice over Fire: Glaciers Carve the Landscape

2000 ◽  
Author(s):  
Robert B. Smith ◽  
Lee J. Siegel
Keyword(s):  
Grand Canyon ◽  
Ice Age ◽  
Yellowstone Lake ◽  
The Past ◽  
North East ◽  
The North ◽  
Jackson Hole ◽  
Teton Range ◽  
Continental Ice Sheets ◽  
Glacial Periods

Yellowstone, the Tetons, and Jackson Hole were shaped by multiple catastrophes. Huge volcanic eruptions and powerful earthquakes played major roles. Finishing touches were added by another kind of calamity: A rare global Ice Age produced gigantic glaciers that buried the landscape with ice two-thirds of a mile thick in places. The glaciers carved mountains, canyons, and lake basins. They dumped large piles of debris and redirected the flow of rivers. The Yellowstone—Teton region is a world-class example of how land was reshaped by glaciers during what is known as the Pleistocene Ice Age. The Ice Age was not a single glacial period, but many intermittent cold spells interspersed with warmer periods during which the ice melted. The timing of major glacial periods is notoriously uncertain. Although continental ice sheets did not quite reach as far south as Yellowstone, a regional icecap and large glaciers covered the Yellowstone—Teton country during three major episodes of at least the past 300,000 years—and perhaps the past 2 million years. The last of these big glaciers retreated about 14,000 years ago, although some argue they did not recede until 10,000 to 12,000 years ago. Today, small glaciers in the Teton Range are found only above 10,000 feet. During each major episode, most of Yellowstone National Park was buried beneath an icecap as much as 3,500 feet thick, among the largest in the ancient Rocky Mountains. Gigantic masses of ice flowed down from the high Yellowstone Plateau, carving and scouring the Earth’s surface, diverting and damming rivers into their present forms, steepening mountain fronts, and deepening lakes. The ice helped sculpt the Grand Canyon of the Yellowstone. More than anything, the thick ice scraped Yellowstone’s volcanic topography, further smoothing the plateau and helping to excavate the basin occupied by Yellowstone Lake. Jackson Hole became a rendezvous of glaciers converging from the north, north-east, and west. Ice up to 2,000 feet thick scooped out the valley floor. The glaciers left tall ridges of rocky debris now covered by lush conifer forests. Such ridges, called moraines, helped shape Jackson Lake.

The Broken Earth: Why the Tetons Are Grand

2000 ◽  
Author(s):  
Robert B. Smith ◽  
Lee J. Siegel
Keyword(s):  
Valley Floor ◽  
The Sun ◽  
Mountain Building ◽  
The West ◽  
The Past ◽  
The North ◽  
The Earth ◽  
Actual Movement ◽  
Jackson Hole ◽  
Teton Range

On a summer morning when the breeze blows cool, it is easy to re the lakes and sagebrush-covered glacial plains of Wyoming’s Jackson Hole sit at nearly 7,000 feet elevation. Yet the altitude of this gorgeous valley is diminished by the view to the west: The precipitous east front of the Teton Range towers above the valley floor, with 13,770-foot Grand Teton and other rugged, snowclad peaks catching the first golden rays of daybreak. This is one of the most spectacular mountain vistas in America. Whether at chill dawn, in glistening light after a torrential afternoon thunderstorm, or during summer evenings when the sun descends behind the lagged Tetons, it is a view that brings solace and peace. Yet the serene splendor of Grand Teton National Park belies a hidden fury. It is not volcanism, which is concealed beneath the gentle pine-covered Yellowstone Plateau to the north. Instead, this defiant topography was born of seismic disaster as the Teton fault repeatedly and violently broke the earth, producing a few thousand magnitude-7 to -7.5 earthquakes during the past 13 million years. During each major jolt, Jackson Hole dropped downward and the Teton Range rose upward, increasing the vertical distance between the valley and the mountains by 3 to 6 feet and sometimes more. Now, after 13 million years of earthquakes, the tallest peaks tower almost 7,000 feet above the valley floor. Actual movement on the fault has been even greater. Jackson Hole dropped downward perhaps 16,000 feet during all those earthquakes. Rock eroded from the Teton Range and other mountains by streams and glaciers filled Jackson Hole with thousands of feet of sediment, disguising how much the valley sank. Combine the uplift of the mountains and the sinking of Jackson Hole, and the best estimate—although still plagued by uncertainty—is that movement on the Teton fault has totaled 23,000 feet during the past 13 million years. That is a tiny fraction of Earth’s 4.6-billion-year history. Consider the effects of repeated episodes of mountain-building during eons before the Teton fault was born: The oldest rocks high in the Teton Range are 2.8-billion-year-old gneisses and schists and 2.4-billion-year-old granites.

scholarly journals Realignments of the Colorado River by ~2 m.y. of rotational bedrock landsliding: The Surprise Valley landslide complex, Grand Canyon, Arizona

Geosphere ◽  
2021 ◽  
Author(s):  
Jesse E. Robertson ◽  
Karl E. Karlstrom ◽  
Matthew T. Heizler ◽  
Laura J. Crossey
Keyword(s):  
Cross Sections ◽  
Colorado River ◽  
Grand Canyon ◽  
Geologic Mapping ◽  
River Level ◽  
The Past ◽  
The North ◽  
Seismic Triggering ◽  
Depositional Age ◽  
Deer Creek

The Surprise Valley landslide complex is the name used here for a group of prominent river-damming landslides in Grand Canyon (Arizona, USA) that has shifted the path of the Colorado River several times in the past 2 m.y. We document a sequence of eight landslides. Three are Toreva-block landslides containing back-rotated but only mildly disrupted bedrock stratigraphy. The largest of these landslides, Surprise Valley landslide, is hypothesized to have dammed the Colorado River, cut off a meander loop through Surprise Valley, and rerouted the river 2.5 km south to near its present course at the Granite Narrows. Another bedrock landslide, Poncho’s runup, involved a mass detachment from the north side of the river that drove a kilometer-scale bedrock slab across the river and up the south canyon wall to a height of 823 m above the river. A lake behind this landslide is inferred from the presence of mainstem gravels atop the slide that represent the approximate spillway elevation. We postulate that this landslide lake facilitated the upriver 133 Mile slide detachment and Toreva block formation. The other five landslides are subsequent slides that consist of debris from the primary slides; these also partially blocked and diverted the Colorado River as well as the Deer Creek and Tapeats Creek tributaries into new bedrock gorges over the past 1 m.y. The sequence of landslides is reconstructed from inset relationships revealed by geologic mapping and restored cross-sections. Relative ages are estimated by measuring landslide base height above the modern river level in locations where landslides filled paleochannels of the Colorado River and its tributaries. We calculate an average bedrock incision rate of 138 m/m.y. as determined by a 0.674 ± 0.022 Ma detrital sanidine maximum depositional age of the paleoriver channel fill of the Piano slide, which has its base 70 m above the river level and ~93 m above bedrock level beneath the modern river channel. This date is within error of, and significantly refines, the prior cosmogenic burial date of 0.88 ± 0.44 Ma on paleochannel cobbles. Assuming steady incision at 138 m/m.y., the age of Surprise Valley landslide is estimated to be ca. 2.1 Ma; Poncho’s runup is estimated to be ca. 610 ka; and diversion of Deer Creek to form modern Deer Creek Falls is estimated to be ca. 400 ka. The age of the most recent slide, Backeddy slide, is estimated to be ca. 170 ka based on its near-river-level position. Our proposed triggering mechanism for Surprise Valley landslides involves groundwater saturation of a failure plane in the weak Bright Angel Formation resulting from large volumes of Grand Canyon north-rim groundwater recharge prior to establishment of the modern Deer, Thunder, and Tapeats springs. Poncho’s and Piano landslides may have been triggered by shale saturation caused by 600–650 ka lava dams that formed 45 river miles (73 river km; river miles are measured along the Colorado River downstream from Lees Ferry, with 1 river mile = 1.62 river kms) downstream near Lava Falls. We cannot rule out effects from seismic triggering along the nearby Sinyala fault. Each of the inferred landslide dams was quickly overtopped (tens of years), filled with sediment (hundreds of years), and removed (thousands of years) by the Colorado River, as is also the potential fate of modern dams.

scholarly journals THE TIME CAPSULE IN THE POST-SOVIET SOVKHOZ

2020 ◽  
Vol 16 (47) ◽  
pp. 84-110
Author(s):  
Elena Malaya ◽  
Keyword(s):  
Temporal Logic ◽  
Soviet Economy ◽  
Soviet Period ◽  
Historical Time ◽  
State Farm ◽  
The Past ◽  
North East ◽  
The North ◽  
Time Capsule ◽  
Post Soviet Period

The article is devoted to ideas about the Soviet era, widespread in а village in the north-east of Crimea. The paper offers an analysis of how the community, formed around a partially preserved state farm, builds its own picture of historical time, expands the imaginary boundaries of the Soviet period, and also thinks of it not so much as the past, but as the past future. Particular attention is paid to the object that organizes its temporality — а time capsule, which was laid twice in the studied village (in 1967 and in 2017), as well as its connection with the teleology of modernism. The article compares letters to descendants, sealed in two time capsules, as well as additional documents sent to the future. The text of the 1967 letter is based on a progressive narrative and contains a list of economic indicators of the success of the Soviet economy. By contrast, the 2017 text creates a picture of an unstable time of change, in which the focus is not on the predictable future, but on the vague past and present. The author of the article explains the nostalgia for the Soviet era in the studied community by the reaction to the changes and crises of the post-Soviet period, and suggests using temporal logic in the research of post-socialism.

scholarly journals Late Holocene temperature variability in Tasmania inferred from borehole temperature data

2017 ◽  
Vol 13 (6) ◽  
pp. 559-572 ◽  
Author(s):  
Asadusjjaman Suman ◽  
Fiona Dyer ◽  
Duanne White
Keyword(s):  
East Coast ◽  
Past Century ◽  
Borehole Data ◽  
Depth Profiles ◽  
The Past ◽  
North East ◽  
The North ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. Thirty-six borehole temperature–depth profiles were analysed to reconstruct the ground surface temperature history (GSTH) of eastern Tasmania for the past 5 centuries. We used the singular value decomposition method to invert borehole temperatures to produce temperature histories. The quality of borehole data was classified as high or low based on model misfit. The quality of the borehole data was not dependent on topography or land use. Analysis reveals that three to five high-quality borehole temperature–depth profiles were adequate to reconstruct robust paleotemperature records from any area. Average GSTH reconstructed from Tasmanian boreholes shows temperature increases about 1.2 ± 0.2 °C during the past 5 centuries. Reconstructed temperatures were consistent with meteorological records and other proxy records from Tasmania during their period of overlap. Temperature changes were greatest around the north-east coast and decreased towards the centre of Tasmania. The extension of the East Australian Current (EAC) further south and its strengthening around the north-east coast of Tasmania over the past century was considered a prime driver of warmer temperatures observed in north-east Tasmania.

scholarly journals ATOP THE KADMEIA: MYCENAEAN ROOF TILES FROM THEBES IN CONTEXT

2020 ◽  
Vol 115 ◽  
pp. 175-245
Author(s):  
Vassilis L. Aravantinos ◽  
Ioannis Fappas ◽  
Yannis Galanakis
Keyword(s):  
Bronze Age ◽  
Fourteenth Century ◽  
Systematic Study ◽  
Late Bronze Age ◽  
Similar Material ◽  
Widespread Distribution ◽  
The Past ◽  
North East ◽  
The North ◽  
First Time

Questions were raised in the past regarding the use of Mycenaean tiles as ‘roof tiles’ on the basis of the small numbers of them recovered in excavations and their overall scarcity in Mycenaean domestic contexts. The investigation of the Theodorou plot in 2008 in the southern part of the Kadmeia hill at Thebes yielded the single and, so far, largest known assemblage per square metre of Mycenaean tiles from a well-documented excavation. This material allows, for the first time convincingly, to identify the existence of a Mycenaean tiled roof. This paper presents the results of our work on the Theodorou tiles, placing emphasis on their construction, form and modes of production, offering the most systematic study of Mycenaean tiles to date. It also revisits contexts of discovery of similar material from excavations across Thebes. Popular as tiles might have been in Boeotia, and despite their spatially widespread attestation, their use in Aegean Late Bronze Age architecture appears, on the whole, irregular with central Greece and the north-east Peloponnese being the regions with the most sites known to have yielded such objects. Mycenaean roof tiles date mostly from the mid- and late fourteenth century bc to the twelfth century bc. A study of their construction, form, production and contexts suggests that their role, apart from adding extra insulation, might have been one of signposting certain buildings in the landscape. We also present the idea that Mycenaean tile-making was guided by a particular conventional knowledge which was largely influenced by ceramic-related technologies (pottery- and drain-making). While production of roof tiles might have been palace-instigated to begin with, it does not appear to have been strictly controlled. This approach to Mycenaean tile-making may also help explain their uneven (in terms of intensity of use) yet widespread distribution.

scholarly journals Variability of stalagmite-inferred Indian monsoon precipitation over the past 252,000 y

2015 ◽  
Vol 112 (10) ◽  
pp. 2954-2959 ◽  
Author(s):  
Yanjun Cai ◽  
Inez Y. Fung ◽  
R. Lawrence Edwards ◽  
Zhisheng An ◽  
Hai Cheng ◽  
...  
Keyword(s):  
North Atlantic ◽  
Southwest China ◽  
Climate Forcing ◽  
Monsoon Precipitation ◽  
Land Bridge ◽  
Global Circulation ◽  
The Past ◽  
The North ◽  
Himalayan Foothills ◽  
Glacial Periods

A speleothem δ18O record from Xiaobailong cave in southwest China characterizes changes in summer monsoon precipitation in Northeastern India, the Himalayan foothills, Bangladesh, and northern Indochina over the last 252 kyr. This record is dominated by 23-kyr precessional cycles punctuated by prominent millennial-scale oscillations that are synchronous with Heinrich events in the North Atlantic. It also shows clear glacial–interglacial variations that are consistent with marine and other terrestrial proxies but are different from the cave records in East China. Corroborated by isotope-enabled global circulation modeling, we hypothesize that this disparity reflects differing changes in atmospheric circulation and moisture trajectories associated with climate forcing as well as with associated topographic changes during glacial periods, in particular redistribution of air mass above the growing ice sheets and the exposure of the “land bridge” in the Maritime continents in the western equatorial Pacific.

New Forms of Work and Employment in an `Old Industrial Region'? The Offshore Construction Industry in the North East of England

1994 ◽  
Vol 8 (4) ◽  
pp. 531-552 ◽  
Author(s):  
Andy Cumbers
Keyword(s):  
Labour Market ◽  
Construction Industry ◽  
Oil And Gas ◽  
Evolutionary Process ◽  
The Past ◽  
North East ◽  
The North ◽  
Local Labour ◽  
New Forms Of Work ◽  
Work And Employment

This paper examines the nature of the new forms of work and employment brought to the North East of England by the development of offshore construction activities, serving the North Sea's oil and gas industries in the period since the early 1970s. In particular, it assesses the extent to which these activities differ from traditional forms of work and employment organisation within the region. The results of this analysis suggest the need to interpret contemporary patterns of restructuring, both in a particular local labour market context and more generally, as part of an on-going evolutionary process, rather than as a decisive break (or shift) from the past.

Little Ice Age fluctuations of Glaciar Río Manso in the North Patagonian Andes of Argentina

2010 ◽  
Vol 73 (1) ◽  
pp. 96-106 ◽  
Author(s):  
M.H. Masiokas ◽  
B.H. Luckman ◽  
R. Villalba ◽  
A. Ripalta ◽  
J. Rabassa
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Lateral Moraine ◽  
Early Nineteenth Century ◽  
The Past ◽  
The North ◽  
Specific Factors ◽  
Subfossil Wood ◽  
Moraine Ridge ◽  
Patagonian Andes

Little Ice Age (LIA) fluctuations of Glaciar R"o Manso, north Patagonian Andes, Argentina are studied using information from previous work and dendrogeomorphological analyses of living and subfossil wood. The most extensive LIA expansion occurred between the late 1700s and the 1830"1840s. Except for a massive older frontal moraine system apparently predating ca. 2240 14C yr BP and a small section of a south lateral moraine ridge that is at least 300 yr old, the early nineteenth century advance overrode surficial evidence of any earlier LIA glacier events. Over the past 150 yr the gently sloping, heavily debris-covered lower glacier tongue has thinned significantly, but several short periods of readvance or stasis have been identified and tree-ring dated to the mid-1870s, 1890s, 1900s, 1920s, 1950s, and the mid-1970s. Ice mass loss has increased in recent years due to calving into a rapidly growing proglacial lake. The neighboring debris-free and land-based Glaciar Fr"as has also retreated markedly in recent years but shows substantial differences in the timing of the peak LIA advance (early 1600s). This indicates that site-specific factors can have a significant impact on the resulting glacier records and should thus be considered carefully in the development and assessment of regional glacier chronologies.

Cuban stalagmite suggests relationship between Caribbean precipitation and the Atlantic Multidecadal Oscillation during the past 1.3 ka

The Holocene ◽  
2012 ◽  
Vol 22 (12) ◽  
pp. 1405-1412 ◽  
Author(s):  
Claudia Fensterer ◽  
Denis Scholz ◽  
Dirk Hoffmann ◽  
Christoph Spötl ◽  
Jesús M Pajón ◽  
...  
Keyword(s):  
North Atlantic ◽  
Little Ice Age ◽  
Rainfall Intensity ◽  
Thermohaline Circulation ◽  
Atlantic Multidecadal Oscillation ◽  
Ice Age ◽  
The Past ◽  
The North ◽  
Southward Shift ◽  
The North Atlantic

Here we present the first high-resolution δ18O record of a stalagmite from western Cuba. The record reflects precipitation variability in the northwestern Caribbean during the last 1.3 ka and exhibits a correlation to the Atlantic Multidecadal Oscillation (AMO). This suggests a relationship between Caribbean rainfall intensity and North Atlantic sea-surface temperature (SST) anomalies. A potential mechanism for this relationship may be the strength of the Thermohaline Circulation (THC). For a weaker THC, lower SSTs in the North Atlantic possibly lead to a southward shift of the Intertropical Convergence Zone and drier conditions in Cuba. Thus, this Cuban stalagmite records drier conditions during cold phases in the North Atlantic such as the ‘Little Ice Age’. This study contributes to the understanding of teleconnections between North Atlantic SSTs and northern Caribbean climate variability during the past 1.3 ka.

scholarly journals A hillfort complex in Myślibórz in the Sudety Mountains

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Ewa Anna Lisowska ◽  
Sylwia Rodak
Keyword(s):  
Sea Level ◽  
Warning System ◽  
Spatial Arrangement ◽  
Archaeological Sites ◽  
Early Medieval ◽  
The Past ◽  
North East ◽  
The North ◽  
Sudety Mountains ◽  
Defensive Sites

The Myślibórz Gorge, located within the Kaczawy Foothills, is well-known to environmentalists and scholars studying the past. The investigations launched in the 1990s made it possible to determine the chronology of three of the archaeological sites in this area. In 2018, two hillforts – on the Kobylica and Golica hills – were investigated. Czech literature classifies such hillforts as the ostrožna-type. The excavations of these hillforts made it possible to establish to date them between the 9th and 10th centuries.The hillforts were located on hilltops with similar altitudes above the sea level, less than 200 m from each other. Such a spatial arrangement made it possible to control the gateway to the Myślibórz Gorge from the north-east. Reasons for developing a defensive system in the southern part of the gorge are obscure, as is the role that two other early medieval hillforts played in it. Was it simply a warning system, or rather part of a comprehensive network of defensive sites?

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