All rights reserved. Another view of the Appalachian Coastal Plain. The MapView section of the NGMDB displays geologic maps from across the country dating back to 1879. As far as reading geologic maps, it’s very helpful to know the time scale and the abbreviations of the different time periods.
A digital version of the King and Beikman (1974) Geologic Map of the United States, originally published at a scale of 1:2,500,000. From the map, you can see that the region is marked by wide color swatches edged by narrow ribbons. by Philip B. The U.S. Geological Survey hosts the National Geologic Map Database (NGMDB). Weird.
Eugene’s in the center of the map . The monoclines formed in the early Cenozoic because of faulting in the underlying basement rock. Because anticlines plunge in the direction of their “noses” (where the outcrop pattern zigs or zags), we can infer that these folds are plunging to the northeast.
“Q” stands for Quaternary-age material (2.5 million years to present), which is typically alluvial material –or sediment deposited by rivers and streams. There is nothing like having actual photographs to understand the concepts.
Thank you! Touring the geologic map of the United States, https://pubs.er.usgs.gov/publication/70136641, http://mapapps.bgs.ac.uk/geologyofbritain/home.html. Lava flows of the Columbia River Basalt Group in eastern Oregon. Rule 4. This interactive tool serves as a national archive for high-quality, standardized geologic maps created by the U.S. Geological Survey and state geological surveys. Just to the south of me lie a variety of older volcanic and sedimentary rocks. Now for some features on the geologic map! Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account.
Aerial view of meander loops on Mississippi River, Louisiana.
The landscape is flat because the lavas are flat –and so they show up as a big swatch of pink. Data resources categorized as geologic maps in the Mineral Resources Online Data Catalog. Take care, and looking forward to reading more from your blog, cheers, Anne , Hi Anne, These rocks include intrusive igneous, undifferentiated metamorphic, and flat-lying sedimentary rock.
The NGMDB also has a similar tool for topographic maps. You can determine the direction the folds plunge by looking at the ages of the rocks: anticlines contain the oldest rock in their cores whereas synclines contain the youngest rocks in their cores. Geologic Map of the United States. The Ogallala Formation (yellow swatch), only about 6-2 million years old and up to 1000 feet in thickness, covers more than 170,000 square miles of the Great Plains –and provides drinking and irrigation water to the vast majority of people in the region.
So, “X, W, Y, Z” are all Precambrian (X=Archean; W, Y, Z=progressively younger Proterozoic); “Pz” means Paleozoic (541-252 million years ago), “Mz” means Mesozoic (252-66 million years ago) “Cz” means Cenozoic (66 million years ago to present). And there are a bunch of intrusive stocks, too. You can see some of these rhyolites at Shoshone Falls in Twin Falls, Idaho. It’s part of the Piedmont, a section of the Appalachians that’s of lower topographic relief than the Valley and Ridge Province, but much more variable in its bedrock geology. The compilation includes new geologic information and state maps, corrections to the original Preliminary Integrated Geologic Map Databases for the United States (PIGMD), and enhancements which are explained in the accompanying report. Published in 1974 by the US Geological Survey, the geologic map of the United States beautifully lays out our country’s geology. Pingback: A US Geology and Art Tour – Dr. Roseanne Chambers, Hello Marli, I just discovered your blog site from a link from another Geology blog which was posted on FB. Change ), You are commenting using your Facebook account. Took me quite a while to figure out what “ITa” means, and why there’s so much of it in Cowlitz Co. Lower Tertiary andesite, for those curious – the Western Cascades? So right here where I am in Eugene, Oregon, I can see that I live on “Q” –which stretches north up the Willamette Valley. Yes– you really do need to have the legend nearby to consult –it helps with so many of the details! In fact, the outcrop widths of vertically dipping beds equals their thickness! Southern Willamette Valley. Change ), You are commenting using your Google account. This post is just an introduction, so I’ll stick to the boxed areas to illustrate some geological relations –and maybe throw in a few photos along the way. Many trips, some quite long (had to get a 6 months multi entry visa! But moving eastward, you hit the Valley and Ridge Province of the Appalachians: long ridges of folded Paleozoic sedimentary rock.