Mysterious Melting of Earth’s Crust in Western North America Investigated by Scientists

Crustal Melting Research

From left, University of Wyoming students Shane Scoggin, Adam Trzinski and Jessie Shields are part of new research investigating crustal melting in western North America. Here, they examine igneous rocks in the Snake Range of Nevada. Credit: Jay Chapman

A group of University of Wyoming professors and students has identified an unusual belt of igneous rocks that stretches for over 2,000 miles from British Columbia, Canada, to Sonora, Mexico.

The rock belt runs through Idaho, Montana, Nevada, southeast California, and Arizona.

“Geoscientists usually associate long belts of igneous rocks with chains of volcanoes at subduction zones, like Mount Shasta, Mount Hood, Mount St. Helens and Mount Rainer,” says Jay Chapman, an assistant professor in UW’s Department of Geology and Geophysics. “What makes this finding so interesting and mysterious is that this belt of igneous rocks is located much farther inland, away from the edge of the continent, and doesn’t contain any evidence for producing volcanoes. In fact, all of the melting to generate the igneous rocks originally took place deep underground, five to 10 miles beneath the surface.”

Chapman is lead author of a paper, titled “The North American Cordilleran Anatectic Belt,” which was published online in February in the journal Earth-Science Reviews. The print version will be published this month.

The paper is a result of a special course taught by Simone Runyon, an assistant professor in UW’s Department of Geology and Geophysics, and Chapman. Runyon, six UW graduate students and one undergraduate student, who took part in the course, are co-authors of the paper.

Cody Pridmore Coyote Mountains

University of Wyoming student Cody Pridmore, who is part of new research investigating crustal melting in western North America, examines igneous rocks in the Coyote Mountains of Arizona. Credit: Jay Chapman

“It was really fascinating to start with a scientific question in a classroom, then collect and analyze data, and eventually publish our results,” says Cody Pridmore, a UW graduate student from Orange, California, and co-author of the paper. “It’s a process most college students don’t get to experience.”

One clue to the origin of the belt of igneous rocks is that the rocks chiefly formed 80 million to 50 million years ago, during a mountain-building event called the Laramide orogeny.

“The Laramide orogeny created most of the major mountain ranges we have in Wyoming, and the name actually comes from the Laramie Range,” Chapman says. “Although there are no igneous rocks of this type and age present in those mountains, we suspect that the tectonic processes that created the mountains also contributed to melting Earth’s crust.”

The researchers have several working hypotheses about what caused the rocks to melt. One hypothesis is that water infiltrated the deep crust.

“The geochemistry of these rocks indicates that melting may have occurred at relatively low temperatures, below 800 degrees Celsius,” says Jessie Shields, a Ph.D. student at UW from Minneapolis, Minn., who is working to solve this mystery. “That is still very hot, but not hot enough to produce very large volumes of magma. Water lowers the melting point of rocks, similar to how salt lowers the melting point of ice, and could increase the amount of magma generated.”

This work has implications for what causes rocks to melt and where specific types of magmas can be found.

“Many of the igneous systems in the study area contain economically important ore deposits,” says Runyon, who specializes in ore deposits. “Understanding the large-scale igneous processes that form these provinces helps us to better understand how ore deposits form and to better explore for natural resources.”

Reference: “The North American Cordilleran Anatectic Belt” by James B. Chapman, Simone E. Runyon, Jessie E. Shields, Brandi L. Lawler, Cody J. Pridmore, Shane H. Scoggin, Nathan T. Swaim, Adam E. Trzinski, Hannah N. Wiley, Andrew P. Barth and Gordon B.Haxel, 24 February 2021, Earth-Science Reviews.
DOI: 10.1016/j.earscirev.2021.103576

The research project is a joint effort involving UW; Andy Barth, a professor at Indiana University-Purdue University Indianapolis; and Gordon Haxel, a U.S. Geological Survey scientist based in Flagstaff, Arizona. Other UW students involved were graduate students Brandi Lawler, of Gordon, Wisc.; Shane Scoggin, of Reston, Va.; Nathan Swaim, of Monument, Colo.; and Adam Trzinski, of Manteno, Ill.; and undergraduate Hannah Wiley, of Sheridan.

3 Comments on "Mysterious Melting of Earth’s Crust in Western North America Investigated by Scientists"

  1. Clyde Spencer | April 23, 2021 at 7:59 am | Reply

    “In fact, all of the melting to generate the igneous rocks originally took place deep underground, five to 10 miles beneath the surface.”

    My first, gut reaction, is that these rocks were emplaced deeper than 5 to 10 miles, despite the inferred low temperature.

    • dr mehrdad sahebzaman iran | January 29, 2024 at 2:18 am | Reply

      Go to the following address and take a look at the structure of the solar system and the history of humans in tens of millions of years ago when they lived and drew the American continent in the form of a bird and South America in the form of a human. God and your Lords and His Lords who sent Jesus and Muhammad and other Prophets and some of our forefathers, God and the Lords of the Earth that Muhammad Mehr observed in Iran have explained to you whether the original language of the Gods and the Lords of the Earth was Farsi and Arabic. The progress that humans had made on earth, their language was Persian and Arabic, why all the important names of the continents are Persian, and some countries have Persian names, and some seas and some cities are Persian? Were they cultivated millions of years ago? For example, why is the name of the country Panama in Farsi? In fact, when you follow the country of Panama to the south, you will see the face of a man whose face and name is a map of the entire continent of South America. In fact, Panama is the foot of a bird, the image of a bird of the North American continent is a wing. His right is Alaska, his left wing is the northeast of the American continent, which is fragmented and there are many islands that are near the North Pole. In every corner of the world, the pictures they drew of the continents, seas, or islands were related to the life of the same creatures in the same environment. which was their place of residence, for example, the island of Papua is in the north of Australia, on this island you can see the image of a dinosaur whose mouth is open and is looking towards the west, and in the Philippines, there is an image of a baby dinosaur that drowned under the water of the ocean, the image of a baby dinosaur is because When the meteorites fell on the earth from the planet that hit the sun and the materials inside the planet after the disintegration of two thousand meters of soil and the elements inside the said planet ten million years ago were spilled over the entire ocean and the surface of the earth and the images that humans have of dinosaurs with shape-shifting The Philippine Islands had given the shape of the Philippine Islands that had been drawn by the dinosaur due to the rise of the ocean water, but in Papua Island, because it was easier to take the soil to that Papua Island, the shape of the dinosaur is clearly visible, but the Philippine Island was more difficult to take the soil to draw. The creation of a dinosaur means that less land was taken, so due to the low height of the Philippine island, the image of the dinosaur under the ocean sunken the Philippine island, which is exactly the shape of a baby dinosaur, but on the island of Papua, the image of the created dinosaur is better visible. They lived, refer to the following address and your comments will be interesting for us. Anyone who has a god above them knows better the history of the earthlings and the fate of the earth. God and the lords of the earth who lived for tens of millions of years know better that they had at least hundreds of thousands of years of civilization. And they have been bred to exist on earth by knowledgeable people, but this is not a matter that we can simply know and be informed. You must gain a lot of experience and research to understand what I have discovered. Be sure to click on the address below and contact us. Be with us, God will protect you dear ones

      2014 – A look back on a significant year for NASA

      • It seems my friend is not well.
        Unfortunately, I am also Iranian and that means I am your compatriot.
        I request those who read the comments of this site not to judge us Iranians by this man’s opinion. For example, I am evolved enough to recognize that the continents were not made by anyone, but formed through a chain of events. Or if our language is a language sent from God and other superstitions, we should not be forced to publish our opinion in the official language of the world.
        I really don’t understand why religious absolutists base their ideas on the discoveries of institutions that usually forbid them, like dinosaurs. Isn’t it already written in the Quran that: And we created the Philippines in the shape of a dinosaur’s head so that Dr. Mehrdad Sahib Zaman can prove himself in the comments of a site?! Finally, I apologize to others if my English is not perfect…

Leave a comment

Email address is optional. If provided, your email will not be published or shared.