Plates aren’t simple – Times-Standard

Plate tectonics is introduced to many children in fifth or sixth grade. Students learn about plate boundaries and how earthquakes, volcanoes and mountain building occur along plate boundaries leaving the interior of plates deformation free.

In California, transform boundaries are given special emphasis with the San Andreas fault as the example close to home. Students might use simple models sliding blocks next to each other and be told that the plates move at about the rate their fingernails grow. They may look at photos or a Google Earth and be asked to pick out the great San Andreas scar that runs most of the length of the state.

It makes a nice story and engaging classroom activities. Unfortunately, it isn’t quite correct. Plate boundaries are more complicated. If all deformation were constrained to the San Andreas, the central and eastern part of the California along with Nevada and Utah would be earthquake free. The 1992 M7.3 Landers earthquake, 1872 M7.8 Lone Pine earthquake and numerous other large historic earthquakes in California and Nevada would never have happened. And I wouldn’t have spent space in recent columns about the recent spurt of activity in Utah, Nevada and Eastern California.

Plate boundaries are constantly evolving. The Pacific-North American plate interaction began about 30 million years ago when the Pacific plate and North American plate first made contact. The San Andreas transform boundary, where plates move horizontally, was formed to accommodate their relative motion. View UC Santa Barbara Professor Tanya Atwater’s animation of how this might have happened below:

(Video not working on mobile? Click here.)

The Pacific and North American plates are enormous pieces of real estate and once the new boundary formed, all did not go smoothly. The enormous pressures caused deformation across the western part of the continent. If you view the Atwater animation, you will get a feel for the distortion across the region.

Not only does stress change as the transform boundary grows, it is interacting with highly heterogeneous rock types. Continents have long, complicated histories. Our continent began to form at least three billion years ago. Over the intervening millennia, it grew as other crust collided into it and lost areas when extensional forces broke split land off. It’s a giant evolving patchwork quilt of rock types with numerous fault and fracture zones of different ages and strengths.

Piecing out the history of this transform boundary has been the collective effort of generations of geologists. In the 19th and much of the 20th century, it was a boots-on-the-ground effort of mapping and analyzing rock units. In the 1970s, paleoseismology opened new ways of reading the recent history of tectonic movements. Paleoseismology has advanced in recent years with GPS studies that allow scientists to measure real time plate motions and LIDAR (laser imaging, detection, and ranging), exposing previously invisible faults.

The picture that has now emerged of the Pacific-North American plate boundary is one that extends all the way to Utah. Don’t worry — the San Andreas is still important. The San Andreas and associated faults such as the San Jacinto in Southern California and the Hayward in Northern California accommodate 75 to 80% of the relative motion between the two plates. But that leaves nearly a quarter of the motion on fault systems to the east — in Eastern California, Nevada and Utah — enough to have a major impact on the landscape.Flying over Nevada and Utah, I am struck by Basin and Range topography, the stark north — south oriented ridges and valleys unobscured by vegetation. Blame the Pacific-North American transform motion. To me they look like giant stretch marks reflecting how the crust thinned in response to the extensional forces. Every one of those ridges is bounded by faults, many capable of producing significant earthquakes. The March 18 M5.7 earthquake in near Salt Lake City, near the edge of the Basin and Range province, is a result of those stresses.

I find the faults and tectonics of Eastern California and Western Nevada even more interesting. Called the Walker Lane or the Eastern California shear zone, this zone extends from the Mojave Desert to just south of Idaho. GPS studies show that it accommodates 10-15% of the total motion between the North American and Pacific plates. Although the sense of motion is similar, Walker Lane is a very different type of beast than the San Andreas, consisting of many different discontinuous faults spread over a 125+ miles wide zone. It doesn’t move homogeneously as different units respond to the stress in different ways. Some blocks even rotate, like the section that produced the recent May 15 M6.5 where the causative fault is nearly perpendicular to the general trend of Pacific-North America motion.

A group of scientists from the University of Nevada, Reno speculate that Walker Lane may eventually kick the San Andreas aside and become the main contributor to the relative motion between the two plates. That might cut off most of California from the North American mainland. Don’t hold your breath or start investing in Western Nevada real estate any time soon. It’s not like to happen for another 7 to 8 million years. Read more at https://www.unr.edu/nevada-today/stories/walker-lane.

What Are The Main Benefits Of Comparing Car Insurance Quotes Online

LOS ANGELES, CA / ACCESSWIRE / June 24, 2020, / Compare-autoinsurance.Org has launched a new blog post that presents the main benefits of comparing multiple car insurance quotes. For more info and free online quotes, please visit https://compare-autoinsurance.Org/the-advantages-of-comparing-prices-with-car-insurance-quotes-online/ The modern society has numerous technological advantages. One important advantage is the speed at which information is sent and received. With the help of the internet, the shopping habits of many persons have drastically changed. The car insurance industry hasn't remained untouched by these changes. On the internet, drivers can compare insurance prices and find out which sellers have the best offers. View photos The advantages of comparing online car insurance quotes are the following: Online quotes can be obtained from anywhere and at any time. Unlike physical insurance agencies, websites don't have a specific schedule and they are available at any time. Drivers that have busy working schedules, can compare quotes from anywhere and at any time, even at midnight. Multiple choices. Almost all insurance providers, no matter if they are well-known brands or just local insurers, have an online presence. Online quotes will allow policyholders the chance to discover multiple insurance companies and check their prices. Drivers are no longer required to get quotes from just a few known insurance companies. Also, local and regional insurers can provide lower insurance rates for the same services. Accurate insurance estimates. Online quotes can only be accurate if the customers provide accurate and real info about their car models and driving history. Lying about past driving incidents can make the price estimates to be lower, but when dealing with an insurance company lying to them is useless. Usually, insurance companies will do research about a potential customer before granting him coverage. Online quotes can be sorted easily. Although drivers are recommended to not choose a policy just based on its price, drivers can easily sort quotes by insurance price. Using brokerage websites will allow drivers to get quotes from multiple insurers, thus making the comparison faster and easier. For additional info, money-saving tips, and free car insurance quotes, visit https://compare-autoinsurance.Org/ Compare-autoinsurance.Org is an online provider of life, home, health, and auto insurance quotes. This website is unique because it does not simply stick to one kind of insurance provider, but brings the clients the best deals from many different online insurance carriers. In this way, clients have access to offers from multiple carriers all in one place: this website. On this site, customers have access to quotes for insurance plans from various agencies, such as local or nationwide agencies, brand names insurance companies, etc. "Online quotes can easily help drivers obtain better car insurance deals. All they have to do is to complete an online form with accurate and real info, then compare prices", said Russell Rabichev, Marketing Director of Internet Marketing Company. CONTACT: Company Name: Internet Marketing CompanyPerson for contact Name: Gurgu CPhone Number: (818) 359-3898Email: [email protected]: https://compare-autoinsurance.Org/ SOURCE: Compare-autoinsurance.Org View source version on accesswire.Com:https://www.Accesswire.Com/595055/What-Are-The-Main-Benefits-Of-Comparing-Car-Insurance-Quotes-Online View photos