Mega‐blowouts in Qinghai–Tibet Plateau: Morphology, distribution and initiation

Abstract

Blowouts are wind‐eroded landforms that are widely distributed in the north‐eastern part in Qinghai–Tibet Plateau (QTP), China. These blowouts are thought to form in response to climate change and/or human activity but little is known about their morphodynamics. Using field surveys, remote sensing and geographic information system (GIS) spatial analysis, the distribution and morphology of blowouts are analysed and their initiation considered. Results show the QTP mega‐blowouts are some of the largest in the world. The orientations of the trough shaped blowouts are parallel with the prevailing wind, but the saucer and bowl‐shaped blowouts are influenced by bi‐directional transport. Whilst regional patterns of blowout shape and size were observed to reflect the extent of aeolian sediments and wind regimes, the relationship between the different morphological parameters showed consistency. During initial stages of development, the length to width ratios of blowouts increase rapidly with area but after they reach a mega size this relationship stabilizes as blowouts widen. Initial luminescence dating shows that blowouts appear to have initiated ~100 to 500 years ago, coinciding with the Little Ice Age (LIA) climate event when northwest winds are known to have intensified. Further work is required to confirm this initiation period and establish the significance of mega blowouts for landscape degradation and human activities. © 2018 John Wiley & Sons, Ltd.

Optimization of UAVs‐SfM data collection in aeolian landform morphodynamics: a case study from the Gonghe Basin, China

“…Wind erosion has induced more serious sandy grassland desertification in this area, and the local ecological environment has faced increasing damage during the past century. Preliminary dating results reveal that blowouts in this area formed hundreds of years ago, coinciding with the Little Ice Age when winds are thought to have been more intense and a drought is known to have occurred (Luo et al, 2019b). Rapid two‐dimensional (2D) extension ratios monitored both by using RTK‐GPS and historical remotely sensed track results prove that land degradation is still ongoing (Luo et al, 2019a).…”

“…There are significant areas of active dunes and wind eroded deflation plains and blowouts in paleo-dunes in the southwest of the Gonghe basin ( Figure 1). Mega-blowouts which have been activated within palaeodunes have seriously destroyed the grassland and threatened the local ecological environmental safety (Luo et al, 2019a(Luo et al, , 2019b. Wind erosion has induced more serious sandy grassland desertification in this area, and the local ecological environment has faced increasing damage during the past century.…”

Blowout Morphometrics and Mass Balances

“…Measuring up to 40 m deep and 1,000 m long (Luo et al, 2019a), the blowouts in Gonghe Basin, Qinghai-Tibet Plateau (QTP) distinguish themselves from previously studied, smaller features in other parts of the world (Hugenholtz and Wolfe, 2006). In comparison to their coastal counterparts, the megablowouts of the QTP defy conventional models of blowout development, exceeding a size in which coastal blowouts would tend towards stabilisation (Hugenholtz and Wolfe, 2009).…”

“…They play a critical role in diagnosing landscape changes, acting as an initial source of sand in reactivating dune fields as well as supplying sediment to downwind features (Barchyn and Hugenholtz, 2013). Blowouts are found in coastal, semi-arid, sandy grassland, and desert landscapes (Hugenholtz and Wolfe, 2006;Hesp and Walker, 2012) and are found across the world, including Europe (van Boxel et al, 1997;Käyhkö, 2007;Gonzlez-Villanueva et al, 2013;Smyth et al, 2013;García-Romero et al, 2019), North America (Fox et al, 2012;Abhar et al, 2015;Garès and Pease, 2015), Africa (Lancaster, 1986), and Asia (Sun et al, 2016;Kang et al, 2017;Luo et al, 2019a). Blowout morphology varies, with scour hollows being classified as saucer, bowl, or trough-shaped and the eroded sediment deposited immediately downwind as either a large lobe or a thinly spread layer of sediment called an apron (Smyth et al, 2020).…”

“…Additional erosion and subsequent destabilisation of the surface, including any anchorage vegetation, then leads to further reductions in surface roughness, and an increasing rate of deflation. Over time, a small area of exposed sand may erode to form a large hollow, supplying sediment to the downwind environment (Luo et al, 2019a). Once initiated, the positive feedback mechanism is selfsustaining and can continue even if conditions are no longer conducive to blowout initialisation (Käyhkö, 2007).…”