The Wasatch Fault, stretching 240 miles along the western edge of the Wasatch Mountains from southern Idaho to central Utah, is a seismically active normal fault that has been a concern for residents in the region. Researchers at Utah State University have made significant discoveries about this complex geological feature, shedding light on why earthquakes occur along the Wasatch Fault and why communities are more vulnerable to earthquake damage than previously thought.

“Normal faults are observed along different tectonic systems, where the tectonic plates are moving apart,” explains geophysicist Srisharan Shreedharan. “The Wasatch Fault forms the eastern edge of the Basin and Range geologic province, which has stretched and broken over millions of years.”

Shreedharan and his team, including Associate Professor Alexis Ault and doctoral student Jordan Jensen, have conducted extensive research on the Wasatch Fault, using rock samples collected from the fault to analyze its properties. Their findings, published in the April 25 online edition of Geology, reveal significant clues about the earthquake risk associated with this geological feature.

One key discovery is that while the Wasatch Fault dips sharply at Salt Lake City, it curves more gently at depth as it moves west and is probably oriented at a much shallower angle at earthquake depth than expected. This means that an earthquake rupture could lead to stronger, more intense shaking at the surface, increasing the likelihood of injury and destruction.

The researchers also found that earthquake slip is possible along the shallowly dipping portion of the Wasatch Fault because the fault rocks themselves are much weaker – worn down and slicker – than the surrounding, undamaged rock. This weak frictional behavior, characterized through deformation experiments and microscopy, is a product of deformation that happened more than 1.7 billion years ago when what is now the Wasatch Fault was at even greater depths within the Earth.

Understanding these findings can help communities along the Wasatch Fault prepare for potential earthquakes and take steps to mitigate damage. As Ault notes, “USU, with its interdisciplinary team of earthquake scientists and engineers, is uniquely positioned to study Utah’s earthquake history, future risks, and help build resilience.”

The research conducted by Shreedharan and his team serves as a reminder of the importance of understanding geological phenomena like earthquakes, which can have devastating consequences for communities. By shedding light on these complex processes, researchers can provide valuable insights that inform policies and practices aimed at reducing earthquake risk and promoting community resilience.

The Western United States is home to some of the most extensive agriculture and growing communities in the country. One of the key factors that sustain these developments is the meltwater from snow-capped mountains, which spills out every spring. For years, models have been used to predict the amount of streamflow available each year, assuming a small fraction of snowmelt enters shallow soil, with the remainder rapidly exiting in rivers and creeks. However, new research from University of Utah hydrologists suggests that this is not the case.

According to their findings, most spring runoff heading to reservoirs is actually several years old, indicating that most mountain snowfall has a long journey as groundwater before it leaves the mountains. This means that there is an order of magnitude more water stored underground than most Western water managers account for, said research leader Paul Brooks.

The team collected runoff samples at 42 sites and used tritium isotope analysis to determine the age of the water. Their findings were published in the journal Nature Communications Earth & Environment and co-authored by Utah geology professors Sara Warix and Kip Solomon in collaboration with research scientists around the West.

Determining the age of mountain streamflow is crucial for predicting how mountain hydrology will respond to changes in climate and land use, according to the researchers. They noted that there would be a lag between input storage and response, which means that even though models have been good in the past, they may not be reliable in the future.

The research also highlighted the importance of incorporating groundwater storage component into models to make good decisions moving forward. Brooks conducted sampling in 2022 while on sabbatical, visiting 42 sites twice, once in midwinter and again during spring runoff.

The state of Utah’s tracking is particularly robust, providing continuous streamflow data dating back 120 years. It’s an unparalleled dataset that has enabled hydrologists to document historic cycles in climate and streamflow that would otherwise have been missed, Brooks said.

According to Solomon, the vast majority of Earth’s fresh, usable water is underground, but just how much is there remains a puzzle. Dating water offers clues, and for determining the age of water, Solomon turns to tritium, a radioactive isotope of hydrogen with a half-life of 12.3 years.

The average age of the runoff sampled in the study varies among the catchment basins depending on their geology. The more porous the ground, the older its water is, since the subsurface can hold a lot more water. By contrast, glaciated canyons with low permeability and shallow bedrock, such as Utah’s Little Cottonwood Canyon, provide far less subsurface storage and younger waters, according to the study.

For decades, federal and state water managers have relied on a network of snowpack monitoring sites to provide data to guide forecasts of water availability for the upcoming year. It’s now clear that such snowpack data doesn’t provide a complete picture, according to the researchers.

“For much of the West, especially the Interior West where this study is based, our models have been losing skill,” Brooks said.

The growing disconnect between snowfall, snowpack volumes and streamflow is driven by variability in these large, previously unquantified subsurface water stores. As a case in point, Brooks highlighted the 2022 water year, which saw snowpacks in many Western states that were near or just below average. Yet that year experienced record low groundwater storage, resulting in much below average spring streamflow.

This new understanding of mountain streamflow has significant implications for water management and resource planning, particularly as the West continues to experience climate variability and change.

The oceans of the Late Jurassic and Early Cretaceous periods were home to some of the most fearsome marine predators on record. Pliosaurs with 2-meter-long jaws, toothy thalattosuchia crocodyliforms, and fast, fish-like ichthyosaurians ruled the seas for millions of years. However, during the middle Cretaceous period, an abrupt change occurred in the fossil record. Ichthyosaurs, thalattosuchians, and pliosaurids suddenly disappeared, while mosasaurs, plesiosaurs, and sharks diversified and expanded.

A recent study has shed new light on what caused this dramatic shift in oceanic top predators. The research team, led by Valentin Fischer of the Université de Liège in Belgium, analyzed data on marine reptile lineages and their extinction patterns during the Cenomanian/Turonian transition, a period associated with high carbon dioxide concentrations and disturbances in ocean nutrients.

The study found that this transition was linked to elevated rates of extinction among large and fast predators. The extinctions were not random but targeted specific groups of top predators in a stepwise manner. For instance, skull shapes of predators changed significantly before and after the transition, resulting in distinct differences in bite force.

This shift in oceanic top predators created unique and somewhat short-lived food webs during the Late Cretaceous period. The study’s findings provide valuable insights into the complex relationships between climate change, ocean anoxia, and the evolution of marine ecosystems. As Fischer notes, “Our analyses showed that the Cenomanian-Turonian transition is associated with elevated rates of extinction and that these extinctions disproportionally targeted some groups of large and fast predators, in a stepwise manner.”