Tag Archives: geology

How the west was made: western North American orogenies

Western North America is a patchwork is hundreds of terranes, which are crustal pieces or microplates (think of islands), that collided with and attached to North America across hundreds of millions of years -- adding piece-by-piece to the continent's width and building mountains as they produced volcanoes or pushed up sediments and rocks. This posts provides a very simplified timeline of the major orogenies and terranes that affected western North America. For a more in-depth look, see the resources below. Read more

Easy Science: How sinkholes form

Sinkholes can form anywhere that the bedrock dissolves away beneath the soil, but classic sinkholes tend to form in limestone, a carbonate rock composed primarily of the minerals calcite (CaCO3), aragonite (CaCO3), and dolomite (CaMg[CO3]2). Worldwide, limestones cover about 15% of land surface. Twenty percent of the US is susceptible to sinkholes. Read more

Volcanic lightning turns ash into glass

Within the ash plumes of explosive volcanic eruptions, collisions among countless pyroclastic particles sometimes lead to the buildup of static charges that discharge dramatically as volcanic lightning. In a new study, researchers have found that this lightning can, in turn, melt and fuse ash particles into distinctive glassy grains called spherules. Identifying and studying these spherules could help scientists better understand past and future eruptions, the study’s authors suggest. Read more

Underwater volcano might be erupting off of Oregon coast

Almost every day for the last five months, hundreds of small earthquakes have rattled Axial Seamount, an underwater volcano located three hundred miles off of the Oregon coast. At the same time, underwater pressure sensors have revealed that the surrounding seafloor had been slowly rising. Then, on April 24, almost eight thousand earthquakes rumbled Axial and the seafloor dropped almost eight feet! Read more

Geologic map reveals US basement rock origins

By combining data about surface mineral resources, national-scale gravity and aeromagnetic surveys, and the age and origins of basement rocks, the USGS has developed a map of the basement rocks underlying the United States. Basement rocks sit above the mantle but beneath all other rocks and sediments. The full report is available here. Read more

The Neanderthal in the karst: hapless skeleton dated at 150,000 years old

During the age of the mammoth, a hominin roaming southern Italy stumbled into a hole in the karst landscape. Out of reach of sun and predator, he starved to death, his body decaying and his bones slumping into a pile, mineral-rich waters ultimately calcifying and fusing them into the surrounding limestone. Locked in the limestone, his skeleton would remain there until 1993, when cave explorers found his face--upside down--staring back at them. Read more

Updated map of ocean floor doubles resolution, reveals volcanoes, spreading centers

Using satellite radar altimetry (which measures elevation) combined with previous data, researchers at UC San Diego have doubled the resolution of the previous decades-old ocean floor map. Large ocean features create a small "bump" in the sea surface above them; for example, a mile high volcano elevates the ocean surface by 10 centimeters. Read more