How Much Water was Needed to Carve the Late Noachian Valley Networks on Mars?

Late Noachian Fluvial Erosion on Mars: Cumulative Water Volumes Required to Carve the Valley Networks and Grain Size of Bed-Sediment

Authors:

Rosenberg et al

Abstract:

Our goal is to quantify the cumulative water volume that was required to carve the Late Noachian valley networks on Mars. We employ an improved methodology in which fluid/sediment flux ratios are based on empirical data, not assumed. We use a large quantity of data from terrestrial rivers to assess the variability of actual fluid/sediment flux sediment ratios. We find the flow depth by using an empirical relationship to estimate the fluid flux from the estimated channel width, and then using estimated grain sizes (theoretical sediment grain size predictions and comparison with observations by the Curiosity rover) to find the flow depth to which the resulting fluid flux corresponds. Assuming that the valley networks contained alluvial bed rivers, we find, from their current slopes and widths, that the onset of suspended transport occurs near the sand-gravel boundary. Thus, any bed sediment must have been fine gravel or coarser, whereas fine sediment would be carried downstream. Subsequent to the cessation of fluvial activity, aeolian processes have partially redistributed fine-grain particles in the valleys, often forming dunes. It seems likely that the dominant bed sediment size was near the threshold for suspension, and assuming that this was the case could make our final results underestimates, which is the same tendency that our other assumptions have. Making this assumption, we find a global equivalent layer (GEL) of 3 – 100 m of water to be the most probable cumulative volume that passed through the valley networks. This value is similar to the ∼34 m water GEL currently on the surface and in the near-surface in the form of ice. Note that the amount of water required to carve the valley networks could represent the same water recycled through a surface valley network hydrological system many times in separate or continuous precipitation/runoff/collection/evaporation/precipitation cycles.

Simulating the Zanclean Pliocene Neogene Flood of the Mediterranean Sea

Computational fluid dynamics simulations of the Zanclean catastrophic flood of the Mediterranean (5.33 Ma)

Authors:

Periáñez et al

Abstract:

Numerical simulations of the Mediterranean Sea filling after the Messinian salinity crisis have been carried out with a two-dimensional non-linear depth-averaged hydrodynamic model. It overcomes simplifications and gross estimates of previous 0-D models. Erosion of the seabed has been implemented in the model domain. The highest erosion rates were found in the Alboran Island passage and in the eastern side of the Strait of Gibraltar. Regressive erosion, at a final stage, can account for the incision channel found in Camarinal Sill. This last limits the inflow to some 90 Sv when the cross-section in the eastern side becomes higher. Water level in the Mediterranean increases at a rate of a few meters per day. Detailed views of the induced circulation in the Mediterranean Sea have also been obtained.

Washington's Scablands Have a Cousin in Iceland

A massive canyon that is home to Europe's most powerful waterfall was created in a matter of days by extreme flooding, new research reveals.

The Jökulsárgljúfur canyon in Iceland, which is 28 km long and 100 metres deep in places, was formed by a series of distinct floods that occurred thousands of years apart, a study shows.

Scientists analysed rocks along a 5km stretch of the canyon - which contains the Jökulsá á Fjöllum river and the mighty Dettifoss waterfall - to create a timeline of how the landscape was created.

They used geochemical analysis to determine how long rocks on the canyon walls had been exposed to the elements. This helped the team pinpoint how the position and shape of the landscape had changed over time.

Researchers connected major shifts in the landscape to a series of extreme floods, which took place 9,000, 5,000 and 2,000 years ago. The floods were caused by volcanic activity under glaciers, and each was powerful enough to tear up bedrock. They formed the canyon's 100-metre walls and pushed three waterfalls, including Dettifoss, back upstream by as much as 2km during each flood.

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Evidence of an Amazon Megaflood in ~ 700 BC?

A 2700 cal yr BP extreme flood event revealed by sediment accumulation in Amazon floodplains

Authors:

Moreira-Turcq et al

Abstract:

Climatic conditions are one of the most important factors affecting hydrological processes in fluvial systems. Higher discharges are responsible for higher erosion, greater transport, and also higher deposition. Consequently, sediment accumulation in Amazonia floodplain river-connected lakes can be directly related to hydrological patterns of the Amazon River mainstream. In this context, we analyzed five sediment cores taken in two floodplain systems situated in the lower Amazon River, to investigate sediment accumulation patterns during the Holocene. Our records show abrupt fluctuations in sedimentation rates in lakes that can reach more than 2 cm/yr during some periods. We find that in all cores, sediment stratigraphy is characterized by packages of sediments of uniform age, which are typically 10–80 cm thick and present a variegated color. The 14C age of the upper package is about 2700 cal yr BP. During this abrupt event, sediment accumulation rates in floodplain lakes can be at least 200 times higher than those of “normal” periods. This sedimentation event is interpreted as being the consequence of one or several successive extreme floods. The 2700 cal yr BP event has been also observed in other sites in South America and other regions in the world, although different impacts can be observed in each system. This event probably corresponds to a conjunction of favorable conditions for extreme Amazon discharge associated with the Middle to Late Holocene increase of austral summer insolation and shifts of the Intertropical Convergence Zone (ITCZ) from northern to southern positions. In this context, a marked negative peak in solar irradiance at 2700 cal yrs BP seems to have provoked cooling on the continents and a southward shift of the ITCZ associated with a probable reduction in the Atlantic Meridian Overturning Circulation.

Evidence of Lake Missoula-like Glacial Lake Drainage From Mid Amazonian Chryse Planitia, Mars

Evidence for Middle Amazonian catastrophic flooding and glaciation on Mars

Authors:

Rodríguez et al

Abstract:

Early geologic investigations of Mars revealed some of the largest channels in the Solar System (outflow channels), which appear to have mostly developed ∼3 byr ago. These channels have been the subject of much scientific inquiry since the 1970s and proposed formative processes included surface erosion by catastrophic floods, glaciers, debris flows and lava flows. Based on the analysis of newly acquired Mars Reconnaissance Orbiter (MRO) Context (CTX, 5.15–5.91 m/pixel) and High Resolution Imaging Science Experiment (HiRISE, 25–50 cm/pixel) image data, we have identified a few locations contained within relatively narrow canyons of the southern circum-Chryse outflow channels that retain well-preserved decameter/hectometer-scale landform assemblages. These terrains include landforms consistent in shape, dimension and overall assemblage to those produced by catastrophic floods, and at one location, to glacial morphologies. Impact crater statistics for four of these surfaces, located within upstream, midstream and downstream outflow channel surfaces, yield an age estimate of ∼600 myr. This suggests that the southern circum-Chryse outflow channels were locally resurfaced by some of the most recent catastrophic floods on the planet, and that these floods coexisted within regional glacier environments as recently as during the Middle Amazonian.

Evidence of Mega Floods on Mars' Athabasca Valles

Megaflood analysis through channel networks of the Athabasca Valles, Mars based on multi-resolution stereo DTMs and 2D hydrodynamic modeling

Authors:

Kim et al

Abstract:

Stereo analysis of in-orbital imagery provides valuable topographic data for scientific research over planetary surfaces especially for the interpretation of potential fluvial activity. The focus of research into planetary fluvial activity has been shifting towards quantitative modeling with various spatial resolution DTMs from visual interpretation with ortho images. Thus in this study, we tested the application of hydraulic analysis with multi resolution Martian DTMs, which were constructed following the approaches of Kim and Muller (2009). Subsequently, a two-dimensional hydraulic model was introduced to conduct flow simulation using the extracted 1.2–150 m resolution DTMs. As a result, it was found that the simulated water flows coincided with what might be water eroded geomorphic features over target areas. Moreover, the information acquired from the modeling, such as water depth along the time line, flow direction and travel time, is proving of great value for the interpretation of surface characteristics. Results highlighted the importance of DTM quality for simulating fluvial channel hydraulics across planetary surfaces.

Aram Chaos are the Channeled Scablands of Mars

Catastrophic ice lake collapse in Aram Chaos, Mars

Authors:

Roda et al

Abstract:

Hesperian chaotic terrains have been recognized as the source of outflow channels formed by catastrophic outflows. Four main scenarios have been proposed for the formation of chaotic terrains that involve different amounts of water and single or multiple outflow events. Here, we test these scenarios with morphological and structural analyses of imagery and elevation data for Aram Chaos in conjunction with numerical modeling of the morphological evolution of the catastrophic carving of the outflow valley. The morphological and geological analyses of Aram Chaos suggest large-scale collapse and subsidence (1500 m) of the entire area, which is consistent with a massive expulsion of liquid water from the subsurface in one single event. The combined observations suggest a complex process starting with the outflow of water from two small channels, followed by continuous groundwater sapping and headward erosion and ending with a catastrophic lake rim collapse and carving of the Aram Valley, which is synchronous with the 2.5 Ga stage of the Ares Vallis formation. The water volume and formative time scale required to carve the Aram channels indicate that a single, rapid (maximum tens of days) and catastrophic (flood volume of 9.3?104 km3) event carved the outflow channel. We conclude that a sub-ice lake collapse model can best explain the features of the Aram Chaos Valley system as well as the time scale required for its formation.

Glacial Lake Atna Megaflood Described

New research indicates that one of the largest fresh-water floods in Earth's history happened about 17,000 years ago and inundated a large area of Alaska that is now occupied in part by the city of Wasilla, widely known because of the 2008 presidential campaign.

The event was one of at least four "megafloods" as Glacial Lake Atna breached ice dams and discharged water. The lake covered more than 3,500 square miles in the Copper River Basin northeast of Anchorage and Wasilla.

The megaflood that covered the Wasilla region released as much as 1,400 cubic kilometers, or 336 cubic miles, of water, enough to cover an area the size of Washington, D.C., to a depth of nearly 5 miles. That water volume drained from the lake in about a week and, at such great velocity, formed dunes higher than 110 feet, with at least a half-mile between crests. The dunes appear on topographical maps but today are covered by roads, buildings and other development.

"Your mind doesn't get around dunes of that size. Obviously the water had to be very deep to form them," said Michael Wiedmer, an Anchorage native who is pursuing graduate studies in forest resources at the University of Washington.

Wiedmer is the lead author of a paper describing the Wasilla-area megaflood, published in the May edition of the journal Quaternary Research. Co-authors are David R. Montgomery and Alan Gillespie, UW professors of Earth and space sciences, and Harvey Greenberg, a computer specialist in that department.

By definition, a megaflood has a flow of at least 1 million cubic meters of water per second (a cubic meter is about 264 gallons). The largest known fresh-water flood, at about 17 million cubic meters per second, originated in Glacial Lake Missoula in Montana and was one of a series of cataclysmic floods that formed the Channeled Scablands of eastern Washington.

The megaflood from Glacial Lake Atna down what is now the Matanuska River to the Wasilla region might have had a flow of about 3 million cubic meters per second. Another suspected Atna megaflood along a different course to the Wasilla region, down the Susitna River, might have had a flow of about 11 million cubic meters per second. The researchers also found evidence for two smaller Atna megafloods, down the Tok and Copper rivers.

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