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 story of human evolution is often tied to the continents we inhabit today – Africa, Asia, and Europe. However, a lesser-known chapter in our planet’s history reveals how the ancient ancestors of elephants, giraffes, humans, and other animals were united across two vast continents due to an extraordinary geological event.

Scientists believe that a plume of hot rocks erupted from the Earth’s mantle 20 million years ago, creating a massive land bridge that connected Asia and Africa through what is now the Arabian Peninsula and Anatolia. This monumental transformation was made possible by the gradual uplift of land, which in turn enabled early humans to roam between continents.

According to research published in Nature Reviews Earth & Environment, this land bridge ended a 75-million-year-long isolation of Africa from other continents, allowing animals to migrate freely between Asia and Africa. The appearance of the land bridge also had significant impacts on ocean circulation and climate patterns.

As reported by lead author Eivind Straume, a postdoctoral fellow at NORCE Norwegian Research Centre and The Bjerknes Centre for Climate Research, “The shallow seaway closed several million years before it otherwise likely would have due to these specific processes – mantle convection and corresponding changes in dynamic topography.” This means that if Africa and Asia had remained separate by an additional million years, the ancestors of humans might have followed a different evolutionary path.

In this case, timing was everything. The primate ancestors of humans came to Africa from Asia before the land bridge fully emerged, only to re-colonize Asia when the two continents were finally connected. This remarkable event is a testament to how the long-term convective evolution of our planet shapes life on Earth.

The uplift of the Arabian Peninsula also had significant impacts on ocean circulation and climate patterns. Nearby ocean temperatures warmed, widening seasonal temperature ranges, making a swath of land from north Africa to central Asia more arid. Researchers believe that this land bridge was the final trigger in making the Sahara a desert. These topographical changes enhanced monsoon season in Asia, making southeast Asia wetter.

This study brings together existing research spanning plate tectonics, mantle convection, topography and paleogeography, evolutionary anthropology, mammal evolution, climate evolution, and ocean circulation to tell a cohesive story of the wide-ranging effects of these mantle dynamics. The findings are a compelling example of how our planet’s history shapes life on Earth.

As study co-author Thorsten Becker, a professor at The University of Texas at Austin Jackson School of Geosciences, said, “This study has relevance to the question of ‘How did our planet change, in general? What are the connections between life and tectonics?'”. The answer lies in the ancient land bridge that united Asia and Africa, shaping animal evolution and climate patterns forever.

The origins of wealth inequality date back further than we often think. According to a groundbreaking study led by Washington State University archaeologist Tim Kohler, disparities in wealth began to emerge more than 10,000 years ago, long before the rise of empires or the invention of writing. This research, published in a special issue of the Proceedings of the National Academy of Sciences, challenges traditional views that inequality suddenly appeared with large civilizations like Egypt or Mesopotamia.

By analyzing data from over 47,000 residential structures across 1,100 archaeological sites worldwide, researchers used house sizes as a measure of wealth. The analysis revealed that wealth inequality started to increase roughly 1,500 years after the advent of agriculture in different civilizations across the world. This effect was driven by population growth, competition for land, and the development of hierarchical settlements.

“Wealth inequality took root surprisingly early,” Kohler said. “The shift wasn’t instantaneous; it grew gradually as societies expanded, populations increased, and resources became more constrained.” The study highlights several key factors contributing to this phenomenon:

1. Land scarcity: As farming communities grew, land became a finite resource, leading to competition and innovations like terracing and irrigation to boost productivity.
2. Larger settlements: These hubs of economic and political activity concentrated wealth in the hands of a few households.
3. Population density: High population settlements exhibited greater inequality than smaller communities.

One significant revelation is that wealth inequality predates written records, with evidence showing disparities existed even in the earliest agricultural societies. By applying the Gini coefficient – a standard measure of inequality – to ancient house sizes, researchers discovered that early farming villages were relatively egalitarian. However, as settlements became larger and more complex, economic disparities grew.

The study also challenges the idea that preindustrial societies lived in a “Malthusian world” of subsistence-level existence. Instead, Kohler and his team found evidence of steady wealth accumulation and technological advancements over millennia. Early agricultural societies often modified their landscapes to intensify production, which increased productivity but widened the gap between those who controlled resources and those who did not.

Some innovations, like iron smelting, reduced inequality by increasing access to tools and resources for lower social strata, challenging the assumption that technological advances always benefit elites. Kohler noted that other factors, such as large governing systems or collaborative social networks, also played a role in mitigating or amplifying inequality over time.

“This isn’t just a modern problem,” Kohler said. “Understanding the origins of wealth inequality helps us see it as a persistent challenge that societies have been grappling with for thousands of years. The past has much to teach us about navigating these issues today.”

The study was a collaborative effort involving 27 researchers from institutions worldwide and was coordinated by the Coalition for Archaeological Synthesis, a not-for-profit organization dedicated to synthesizing the archaeological record to advance science and benefit society. By focusing on the period before written records, the researchers hope to fill a critical gap in understanding how human societies evolved, from egalitarian hunter-gatherer groups to complex, hierarchical communities.

“These patterns are deeply embedded in our history,” Kohler said. “But by studying them, we can better address their implications for the future. If we can understand how inequality emerged and evolved, perhaps we can learn how to mitigate its impact today.”