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POTD April 25, 2014: Dixie National Forest, Iron County, Utah

Have a great weekend everyone!

Dixie National Forest, Iron County, Utah
Photographer: Robert F. Biek; © 2012

Hancock Peak (elevation 10,598 feet) is one of many cinder cones that dot the Markagunt Plateau east of Cedar City. Engelmann spruce trees, many of which were killed by spruce bark beetles, and colorful quaking aspen blanket the cinder cone and associated lava flow, which are estimated to be about 600,000 years old.

Geologic investigation into fatal rock fall in Rockville risk remains high

sunews.net

Residents living within high rock-fall-hazard zones in Rockville, Utah, face the possible consequences of a large rock fall similar to the fatal event that occurred last December.

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UGS presents new report to water district

ironcountytoday.com

Cracks in the earth and settling of the ground in areas of the Cedar Valley, both believed to be caused by over-pumping of the underground aquifer, were the focus of a special Central Iron County Water Conservancy District work meeting March 27.

To find the publication, visit the Utah Natural Resources Map & Bookstore, or find it online HERE.

Report: Ground sinking around Cedar City (Interview)

Watch these interviews featuring one of our geologists, Tyler Knudsen, talk about the ground fissures and their causes.

fox13now.com

Giant cracks running through an Iron County subdivision are the result of drawing too much water from the ground, according to a new state report.

WATCH HERE

Report: Cedar Valley Ground Slowly Sinking

kutv.com

A new report from the Utah Geological Survey shows that the ground in Iron County’s Cedar Valley is slowly sinking due to groundwater pumping.

WATCH HERE

Groundwater depletion sinks portions of Cedar Valley

deseretnews.com

Over-pumping of groundwater from a deep aquifer in Cedar Valley for the past three decades has caused the ground to sink and crack, inflicting damage on a would-be subdivision and putting future development at risk.

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Read further in this article from KCSG Television

Land Subsidence and Earth Fissures in Cedar Valley, Iron County, Utah

kcsg.com

A just-released report from the Utah Geological Survey (UGS) shows the ground has been sinking in some areas around Cedar City for decades. The comprehensive 116-page report presents the results of an investigation of land subsidence and earth fissures in Cedar Valley, Iron County, Utah, primarily due to groundwater pumping. “The sediments in the Cedar Valley that form the groundwater aquifer contain a significant amount of fine-grained silt and clay sediments. Those sediments become compacted when water is removed and the ground begins to sink,” said Tyler Knudsen, UGS project geologist.

Investigation of Land Subsidence and Earth Fissures in Cedar Valley, Iron County, Utah

By: Tyler Knudsen, Paul Inkenbrandt, William Lund, Mike Lowe, and Steve Bowman

This 116-page report presents the results of an investigation by the Utah Geological Survey of land subsidence and earth fissures in Cedar Valley, Iron County, Utah. Basin-fill sediments of the Cedar Valley Aquifer contain a high percentage of fine-grained material susceptible to compaction upon dewatering. Groundwater discharge in excess of recharge (groundwater mining) has lowered the potentiometric surface in Cedar Valley as much as 114 feet since 1939. Groundwater mining has caused permanent compaction of fine-grained sediments of the Cedar Valley aquifer, which has caused the land surface to subside, and a minimum of 8.3 miles of earth fissures to form. Recently acquired interferometric synthetic aperture radar imagery shows that land subsidence has affected approximately 100 mi² in Cedar Valley, but a lack of accurate historical benchmark elevation data over much of the valley prevents its detailed quantification. Continued groundwater mining and resultant subsidence will likely cause existing fissures to lengthen and new fissures to form which may eventually impact developed areas in Cedar Valley. This report also includes possible aquifer management options to help mitigate subsidence and fissure formation, and recommended guidelines for conducting subsidence-related hazard investigations prior to development.

Although this product represents the work of professional scientists, the Utah Department of Natural Resources, Utah Geological Survey, makes no warranty, expressed or implied, regarding its suitability for a particular use. The Utah department of Natural Resources, Utah Geological Survey, shall not be liable under any circumstances for any direct, indirect, special, incidental, or consequential damages with respect to claims by users of this product.

GET IT HERE

Interim Geologic Map of the Enoch Quadrangle, Iron County, Utah

By: Tyler R. Knudsen

The Enoch quadrangle, in eastern Iron County, Utah, includes the northeastern part of Cedar Valley and parts of the adjacent Red Hills. The Red Hills-structurally consisting of an elevated, fault-bounded horst block-expose the upper parts of the Tertiary Claron Formation as well as a chaotic mass of Miocene and Oligocene volcanic rocks that may be part of the Markagunt Megabreccia that is widely exposed on the central and northern Markagunt Plateau to the east. Basaltic andesite flows cover large parts of the North Hills in the northeastern part of the quadrangle. Earth fissures related to groundwater overdraft of the Cedar Valley aquifer and resultant land subsidence have formed along parts of the eastern and western margins of the Enoch graben.

This CD contains two plates-a geologic map at 1:24,000 scale and an explanation plate-and a 12-page booklet, all in PDF Format. The latest version of Adobe Reader is required to view the PDF files.

GET IT HERE

Interim Geologic Map of the Cedar City NW Quadrangle, Iron County, Utah

By: Tyler R. Knudsen and Robert F. Biek

The Cedar City NW quadrangle includes the southwestern part of Cedar Valley and parts of the adjacent Eightmile Hills and Granite Mountain in Iron County, Utah. Exposed strata range from the Jurassic Temple Cap Formation to Oligocene-age quartz monzonite of the Granite Mountain laccolith. Emplacement of the Granite Mountain and Three Peaks laccoliths was controlled by the east-verging Sevier-age Iron Springs Gap thrust fault. Replacement manetite-hematite ore bodies in the Co-op Creek Limestone Member exist locally along the margins of the laccoliths and have made the Iron Springs mining district the largest iron-producing district in the western U.S. In the Eightmile Hills, regional ash-flow tuffs are locally involved in a large gravity slide shed off the Granite Mountain laccolith. Earth fissures related to groundwater overdraft of the Cedar Valley aquifer and resultant land subsidence have formed north and west of Quichapa Lake.

This CD contains two pates-a geologic map at 1:24,000 scale and an explanation plate-and a 18-page booklet, all in PDF format. The latest version of Adobe Reader is required to view the PDF files.

GET IT HERE

Interim Geologic Map of the Cedar City 7.5-Minute Quadrangle, Iron County, Utah

By: Tyler R. Knudsen

The Cedar City 7.5′ quadrangle is roughly centered on the rapidly-growing community of Cedar City in Iron County, Utah. It straddles the boundary between the Basin and Range and Colorado Plateau physiographic provinces, which at the latitude of the quadrangle, is defined by the north-south-trending Hurricane fault. The eastern half of the quadrangle encroaches on the western margin of the Markagunt Plateau (Colorado Plateau). Rocks there are mostly Mesozoic in age, and have been moderately to highly deformed by Sevier-age thrusting and folding and by later basin-and-range-style normal faulting. The western half of the quadrangle lies in Cedar Valley, a typical Basin and Range basin filled with hundreds to thousands of feet of unconsolidated basin-fill sediments and basaltic lava flows.

This CD contains two plates-a geologic map at 1:24,000 scale and an explanation plate-and a 20-page booklet, all in PDF format. The latest version of Adobe Reader is required to view the PDF files.

GET IT HERE

Geologic Map of The Brian Head Quadrangle, Iron County, Utah

By: Peter D. Rowley, Robert F. Biek, Edward G. Sable, Jonathan T. Boswell, Garrett S. Vice, Stanley C. Hatfield, David J. Maxwell, and John J. Anderson

The Brian Head Quadrangle straddles the west edge of the Markagunt Plateau and is roughly centered on Brian Head Peak, at 11,307 feet (3446 m) the highest mountain in southwestern Utah. The peak, encompassing an area of great natural beauty and recreational use, is capped by volcanic rocks that erupted from calderas on the Utah-Nevada border. These volcanic rocks overlie landslide-prone local volcaniclastic strata, which in turn overlie colorful strata of the Claron Formation, centerpiece of Cedar Breaks National Monument in the southwest corner of the map area. The plateau is capped by remnants of the 20-million-year-old Markagunt Megabreccia, Utah’s largest catastrophic gravity slide.

This CD contains geographic information system (GIS) files in ESRI file geodatabase and shapefile formats. Two plates, a geologic map at 1:24,000 scale and an explanation plate, and a 38-page booklet are also included in PDF format. The latest version of Adobe Reader is required to view the PDF files.

GET IT HERE