Northern Oregon Coast Range

Geology

The origins of these mountains began approximately 40 million years ago during the Eocene age. During this time-period, sandstone and siltstone formed in the area. Additionally, igneous rocks and basalt flows combined with basaltic sandstone to create many of the mountainous formations. Other sedimentary rock in the area formed more recently, around 20 million years ago. It is hypothesized that portions of the northern section of the range were islands during parts of the Eocene era. Other portions of the mountains consist of marine sedimentary rock. The entire coast range sits on a convergent tectonic margin interacting with the Juan de Fuca Plate that is subducting beneath North America tectonic plate. Also, weathering and erosion of the region is a major factor in shaping the landscape. Heavy rainfall and landslides have worked to alter the mountains.

The range is part of a broad, plunging structural arch of sedimentary and Tertiary volcanic strata that is being uplifted. Eocene and Miocene sections form the flanks of the uplifted sections. Some of the oldest rocks are submarine tholeiitic basalts from the Eocene era. The basalt came from the basalt flows that covered much of Oregon and originated from volcanoes in the central portion of the state. Other rocks include sandstone, mudstone, and siltstone. It was during the middle Miocene period that the range was uplifted in the broad, northeast-plunging arch.

Flora and fauna

Portions of the range are in the Siuslaw National Forest and Tillamook State Forest, and large sections of the range were burned in forest fires during the 1930s and 1940s as part of the Tillamook Burn. In the forested areas trees include Sitka spruce, western redcedar, Douglas fir, and western hemlock. Other plants that grow in the region are huckleberry, salmonberry, thimbleberry, salal, vine maple, sword and bracken ferns and Oregon grape to name a few.

Arthropods and molluscs found include collembolans, spiders, beetles, slugs, millipedes, weevils, and various centipedes. Animals that inhabit the Northern Coast range are the rough-skinned newt, chipmunks, bears, rabbits, white-footed deer mice, Columbian black tail deer and others. Birds include chickadees, red-breasted nuthatches, kinglets, Western pileated woodpeckers, Oregon Canada jays, California creepers, and Sitka red crossbills among others.

Location and climate

The range begins at the Columbia River, with some mountainous features on the north side of the river, and continues south roughly 100 mi to the Salmon River where Oregon Route 18 traverses the range from the Willamette Valley to the Oregon Coast. The width of the range varies but is roughly 35 mi.

The climate of the range is moderate because of marine influences, and annual precipitation is heavy, varying from 60 to.

Peaks

All mountains over 3000 ft in elevation in the Northern Coast Range.

Other peaks

• Round Top (Oregon) 2982 ft
• Neahkahnie Mountain 1634 ft

Rivers

The following rivers have their headwaters in the Northern Oregon Coast Range:

• Drains to Columbia River:
  • Clatskanie River
  • John Day River
  • Klaskanine River
  • Lewis and Clark River
  • Skipanon River
  • Wallooskee River
  • Youngs River
• Drains to Willamette River:
  • Tualatin River
  • Yamhill River
• Drains to Pacific Ocean:
  • Kilchis River
  • Miami River
  • Necanicum River
  • Nehalem River
  • Nestucca River
  • Salmonberry River
  • Salmon River
  • Tillamook River
  • Trask River
  • Wilson River

References

References

1. [http://www.peakbagger.com/peak.aspx?pid=1075 Rogers Peak.] Peakbagger.com. Retrieved February 29, 2008.
2. [http://www.fsl.orst.edu/ncama/guidch2.htm Northern Coast Range Adaptive Management Area; Chapter 2: Physical and Biological Environment.] Oregon State University. Retrieved February 29, 2008.
3. [http://www.oregon.gov/ODF/STATE_FORESTS/docs/Watershed/Nehalem_Watershed_Analysis/Part_I-Ch_1-4.pdf Upper Nehalem Watershed Analysis.] (PDF) Oregon Department of Forestry. Retrieved February 29, 2008.
4. Byrne, John V. "An Erosional Classification for the Northern Oregon Coast", ''Annals of the Association of American Geographers'', Vol. 54, No. 3. (Sep. 1964), pp. 329–335.
5. [http://www.wou.edu/las/natsci_math/geology/luckiamute/Appendix%20A%20Geology%20of%20Luckiamute%20River%20Watershed.pdf Geology of the Luckiamute River Watershed, Upper Willamette Basin, Polk and Benton Counties, Oregon.] (PDF) Western Oregon University. Retrieved February 29, 2008.
6. [https://pubs.usgs.gov/of/1994/of94-021/tilgeo.txt Geologic Map of the Tillamook Highlands, Northwest Oregon Coast Range.] U.S. Geological Survey. Retrieved February 29, 2008.
7. [http://www.treedictionary.com/DICT2003/hardtoget/jk-64-html/index.html From the Forest to the Sea: A Story of Fallen Trees.] Tree Dictionary. Retrieved February 29, 2008.
8. Macnab, James A. Biotic Aspection in the Coast Range Mountains of Northwestern Oregon. ''Ecological Monographs'', Vol. 28, No. 1. (Jan. 1958), pp. 21–54.
9. [http://www.oregon.gov/ODF/PRIVATE_FORESTS/docs/Legacy/AppendixA.pdf Private Forests.] Oregon Department of Forestry. Retrieved February 29, 2008.