Geologists solves 40 years of discussion on the strength of Olivine, a magnesium iron silicate, one of Earth’s most common minerals.
Tectonic plates used to explain the location of volcanoes and earthquakes. The strength of olivine found in the upper 250 miles or so of the Earth, known as the mantle.
Measuring the strength of olivine is critical to understanding how strong tectonic plates are, which in turn how plates break and create subduction zones, said, University of Delaware professor Jessica Warren. It’s also important for understanding how plates move around over the million-year time scales.
strength of Olivine
The researchers used a technique, called instrumented nanoindentation, to measure olivine’s strength. The technique recreate pressure conditions like those inside the earth by pressing a diamond tip that was carefully machined to a specific geometry into the olivine crystal to measure the material’s response. The diamond tips ranged in size from 5 to 20 microns. The researchers performed hundreds of indentation tests and found that the olivine crystal became weaker as the size of the diamond tip increased.
To validate this size-effect, the researchers determine the sizes and areas that tested in previous experiments dating to the late 1970s. The size-effect showed up in the old data, too.
Now researchers turning their attention to how temperature affects the strength of olivine. Temperatures inside the earth has much hotter than on the surface and can range from 1,470 to 2,200 degrees Fahrenheit.
The team also considers the role of water in the structure of olivine minerals and rocks in the earth.
“When geologists look at how faults buckle and deform. It is at a very small length scale where conditions in size effect really matter,” Warren said.
More information: [Science Advances]