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Margaret Hiza Redsteer

Publications and source records attributed to Margaret Hiza Redsteer.

7 recordsLinked to original sources
USGS2021

Landscape evolution in eastern Chuckwalla Valley, Riverside County, California

This study investigates sedimentary and geomorphic processes in eastern Chuckwalla Valley, Riverside County, California, a region of arid, basin-and-range terrain where extensive solar-energy development is planned. The objectives of this study were to (1) measure local weather parameters and use them to model aeolian sediment-transport potential; (2) identify surface sedimentary characteristics in representative localities; and (3) evaluate long-term landscape evolution rates and processes by analyzing stratigraphy in combination with luminescence geochronology. The new stratigraphic and geochronologic data presented in this report demonstrate the varying local significance of aeolian, alluvial fan, lacustrine (playa), and possibly Colorado River influence over a range of time scales. The dominant sand-transport direction in eastern Chuckwalla Valley is toward the northeast, consistent with the recognized regional west-to-east wind direction. However, occasional strong wind events from the north can transport large quantities of sand southward and temporarily reshape local geomorphic features. Influence of a northwest wind direction is also locally dominant around mountain ranges and controls the modern morphology of the Palen dune field. Modeled sand fluxes are on the order of 10 5 kilograms per meter width per year at the site of weather monitoring, 5 kilometers northwest of the Mule Mountains. Aeolian dunes are locally well developed and actively migrating. Their location and activity are determined largely by sediment supply from playa surfaces and ephemeral stream channels, which also control the dunes’ spatial extent and migration potential; stream channels act as both source and sink for aeolian sediment in this environment. Excavations at five sites along a northwest-to-southeast transect reveal that playa deposits formed around 266–226 thousand years ago south of the McCoy Mountains and immediately north of the present location of Interstate 10. The playa material is overlain by late Pleistocene to Holocene alluvial fan deposits. To the southeast (south of Interstate 10, but north of the Mule Mountains), we identified rapid accumulation of alluvial sediment around the time of the Last Glacial Maximum (23–20 thousand years ago), unconformably overlain by a locally varying assemblage of recent aeolian material or Holocene alluvial fan sediment. We have used stratigraphic characteristics and luminescence ages to calculate accumulation rates for sites in eastern Chuckwalla Valley, and thereby to identify spatial variation in landscape stability over decadal and longer time scales. If future solar-energy development plans are to include natural sand-transport corridors, plans would entail retaining the ability for sand to be transported eastward from the ephemeral stream channels and playas that supply sediment to the dunes, sand sheets, and sand ramps of Chuckwalla Valley, and also to allow for southward transport during episodic strong weather events several times per year. The aeolian sediment-transport corridors are dynamic spatially and temporally, reorganizing on the basis of seasonal changes to wind drift potential. Future landscape stability also will be determined by climate-driven changes to vegetation and thereby to aeolian sediment availability. In a warmer, drier climate, aeolian sediment activity is expected to increase, owing to a decrease in stabilizing vegetation cover and more extreme rain that supplies sediment to ephemeral stream channels and playas from which it is remobilized by wind.

California↗
USGS2015

Field measurement and analysis of climatic factors affecting dune mobility near Grand Falls on the Navajo Nation, southwestern United States

Aeolian sand covers extensive areas of the Navajo Nation in the southwestern United States. Much of this sand is currently stabilized by vegetation, although many drier parts of these Native lands also have active and partly active dunes. Current prolonged drought conditions that started in the mid-1990s are producing significant changes in dune mobility. Reactivation of regional aeolian deposits due to drought or increasing aridity from rising temperatures resulting from climate change could have serious consequences for human and animal populations, agriculture, grazing, and infrastructure. To understand and document the current and future potential for mobility, seasonally repeated surveys were used to track the location of multiple active barchan dunes. By utilizing Real-Time Kinematic GPS field surveys and simultaneously collecting in-situ meteorological data, it is possible to examine climatic parameters and seasonal variations that affect dune mobility and their relative influences. Through analysis of the recorded data, we examined the fit of various climate parameters, and demonstrate that under the current prolonged drought, wind power is the dominant factor controlling dune mobility.

Arizona↗
USGS2013

Recent seasonal variations in arid landscape cover and aeolian sand mobility, Navajo Nation, southwestern U.S.

The socioeconomic impacts of climate change pose problems not only in devel- oping countries but also to residents of arid lands in the United States among marginalized societies with limited economic means. In the Navajo Nation, warming temperatures and recent drought have increased aeolian sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. Dust derived from this region also affects albedo and longevity of the Rocky Mountains snowpack, located downwind. We present initial results from a study that monitors sand transport and vegetation within a 0.2 km2 site in the Navajo lands, measuring the effects of drought on landscape stability since 2009. Sand mobility decreased substantially as 1 year with near-normal monsoon rainfall (2010) somewhat abated a decade-long drought, temporarily doubling vegetation cover. Vegetation that grew during 2010, with adequate rain, died off rapidly during dry conditions in 2011. Short-term increases in rainfall that promote annual, but not perennial, plant growth will not improve landscape stability in the long term. Climate projections suggest that a warmer, drier climate and potentially enhanced sediment supply from ephem- eral washes will further increase aeolian sand transport and dune activity, worsening the present challenges to people living in this region. Connections among climate, vegetation, and aeolian sediment erodibility in this region are highly relevant to other areas of the world with similar environmental problems.

Arizona↗
USGS2013

Geologic map of the Winslow 30’ × 60’ quadrangle, Coconino and Navajo Counties, northern Arizona

The Winslow 30’ × 60’ quadrangle encompasses approximately 5,018 km 2 (1,960 mi 2 ) within Coconino and Navajo Counties of northern Arizona. It is characterized by gently dipping Paleozoic and Mesozoic strata that dip 1° to 2° northeastward in the southwestern part of the quadrangle and become nearly flat-lying in the northeastern part of the quadrangle. In the northeastern part, a shallow Cenozoic erosional basin developed about 20 million years ago, which subsequently was filled with flat-lying Miocene and Pliocene lacustrine sediments of the Bidahochi Formation, as well as associated volcanic rocks of the Hopi Buttes Volcanic Field. The lacustrine sediments and volcanic rocks unconformably overlie Triassic, Jurassic, and Cretaceous strata. Beginning about early Pliocene time, the Little Colorado River and its tributaries began to remove large volumes of Paleozoic and Mesozoic bedrock from the map area. This erosional development has continued through Pleistocene and Holocene time. Fluvial sediments accumulated episodically throughout this erosional cycle, as indicated by isolated Pliocene(?) and Pleistocene Little Colorado River terrace-gravel deposits on Tucker Mesa and Toltec Divide west of Winslow and younger terrace-gravel deposits along the margins of the Little Colorado River Valley. These gravel deposits suggest that the ancestral Little Colorado River and its valley has eroded and migrated northeastward toward its present location and largely parallels the strike of the Chinle Formation. Today, the Little Colorado River meanders within a 5-km (3-mi) wide valley between Winslow and Leupp, where soft strata of the Chinle Formation is mostly covered by an unknown thickness of Holocene flood-plain deposits. In modern times, the Little Colorado River channel has changed its position as much as a 1.5 km (1 mi) during flood events, but for much of the year the channel is a dry river bed. Surficial alluvial and eolian deposits cover extensive parts of the bedrock outcrops over the entire Winslow quadrangle.

Arizona↗
USGS2012

Vegetation, substrate, and eolian sediment transport at Teesto Wash, Navajo Nation, 2009-2012

On the Navajo Nation, southwestern United States, warming temperatures and recent drought have increased eolian (windblown) sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. We present an assessment of seasonal variations in sand transport, mobility, and ground cover (vegetation and substrate) within a 0.2-km 2 study area near Teesto Wash, southern Navajo Nation, as part of a multiyear study measuring the effects of drought on landscape stability. Sand mobility in the study area decreased substantially as one year (2010) with near-normal monsoon rainfall somewhat abated a decade-long drought, temporarily doubling vegetation cover. The invasive annual plant Russian thistle ( Salsola sp.), in particular, thrived after the monsoon rains of 2010. Vegetation that grew during that year with adequate rain died off rapidly during drier conditions in 2011 and 2012, and the proportion of bare, open sand area increased steadily after summer 2010. We infer that isolated seasonal increases in rainfall will not improve landscape stability in the long term because sustained increase in perennial plants, which are more effective than annual plants at stabilizing sand against wind erosion, requires multiple consecutive seasons of adequate rain. On the basis of climate projections, a warmer, drier climate and potentially enhanced sediment supply from ephemeral washes may further increase eolian sediment transport and dune activity, worsening the present challenges to people living in this region. Connections between climate, vegetation cover, and eolian sediment erodibility in this region also are highly relevant for studies in other regions worldwide with similar environmental characteristics.

Navajo Nation, Teesto Wash↗
USGS2011

Monitoring and analysis of sand dune movement and growth on the Navajo Nation, southwestern United States

Recurring drought and rising temperatures have caused reactivation and renewed growth of sand dunes on the lands of the Navajo Nation on the Colorado Plateau. Migrating dunes threaten health, housing, and transportation pathways. U.S. Geological Survey (USGS) scientists are conducting research to better understand the processes of dune growth and movement. This research will provide critical data to the Native peoples of the region in their response to the changing environment.

Colorado Plateau↗
USGS2011

A dryland river transformed—the Little Colorado, 1936–2010

The Little Colorado River, in northeastern Arizona, is a major tributary of the Colorado River. Over a span of 74 years, the U.S. Geological Survey (USGS) has mapped substantial migration of the river channel between the City of Winslow and the Navajo Nation community of Leupp (Tólchíí kooh). In a human lifetime, the river has moved more than 1 mile across its valley floor. Channel migration and flooding pose a considerable risk to the life and property of people living near the river. USGS scientists are working to better understand the potential for further channel adjustments and flooding to help provide communities at risk with the information they need to address these threats and make future development decisions.

Arizona↗