Master Index    Nearest Caches Submerged River Valley - Upper Newport Bay by TerryDad2 (1/1) N33° 39.175  W117° 53.015 (WGS84) UTM  11S   E 418071  N 3724023 Use waypoint: GCPFR5 Size: Not chosen    Hidden on 6/27/2005 In California, United States Difficulty:     Terrain:

The Upper Newport Bay is thought to have formed 300,000 years ago when sea levels were lower than they are now due to a glacial period. At that time, geologists estimate that this area received about 80 inches of rain a year. This likely produced year-round flow in the ancient Santa Ana River that flowed through the channel below you and southward beneath Upper Newport Bay.

At that time, the river would have flowed though a flat flood plain. Had any of the hills you see around you today existed, the river would have taken a different course. After the river had eroded out a stable course, the Newport Mesa and San Joaquin Hills began to slowly uplift as a result of movement along the Newport-Inglewood fault zone. Flow in ancient Santa Ana River was able to maintain its course throughout the uplift by eroding the land faster than it was uplifted. This resulted in the steep cliffs you see surrounding the bay, such as the 100 foot cliffs across the bay to the east.

Rising sea levels completely submerged the bay until about 15,000 to 25,000 years ago. This submersion effectively stopped the continued erosion of the river channel as the Newport Mesa continued to rise. While the bay was submerged, the ancient Santa Ana River also found a new path emptying into the ocean at Alamitos Bay.

Recent lining of the creeks that continue to drain into the Upper Newport Bay has resulted in the filling in of the bay with more sediment than would be expected in a natural system. As a result the bay has been dredged to maintain its current configuration.

Filling in of bays is a natural process, but not at the rate that had been observed in the years since the area was urbanized. Natural processes would eventually fill in the bay, turning it into a marsh, then open grass land if allowed to continue.

Logging Requirement: Send me a note explaining what features of the drainage channel that the bridge crosses over has contributed to the speed that the bay has been filling. What features are seen in other flood control channels throughout the watershed.
Please begin your e-mail with the name of the earthcache and be sure your log indicates how many people were in your group.

The following sources were used to generate this cache. None of this cache was original work.

• Colburn, Ivan P. (California State University, Los Angeles) THE ROLE OF ANTECEDENT RIVERS IN SHAPING THE SOUTHERN CALIFORNIA COAST, AAPG Pacific Section / SPE Western Regional Joint Meeting, May 19-24, 2003, Long Beach, California, U.S.A. (Abstract only)
• Norris, Robert M. Robert W. Webb, Geology of California Second Edition, John Wiley & Sons, Inc. 1990
• http://www.ocparks.com/uppernewportbay/default.asp?Show=History
• Image Source: EagleAerial July, 2003

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Additional Hints (There are no hints for this cache)

5/23/2008 by Wild Coin Cacher
Nicely incised channel on a great walking path. TFTC sent email.

5/23/2008 by Cacheflyer
We were hopping the weather would be better today, but no luck. It didn't stop us on our caching around Huntington Beach trip. Thanks for bringing me to this spot and I enjoyed reading the info. on the cache's page. Email sent via Wild Coin Cacher. TFTC SL

5/15/2008 by Peasinapod
A nice bit of geology. Thanks!

4/7/2008 by chiefsfan19
Thanks, enjoyed the views and the history lesson. Took some pictures and posted them. email sent with info.
TFTC

4/4/2008 by mike2find
Great view with all the wildlife around. TFTC

3/29/2008 by jeffnbev
Thanks for pointing our the history of the river valley .... Been here many times ... now with a new perspective

Message on the way

3/21/2008 by Hill 1
Out n’ about in the Upper Newport Bay area, with my significant other, trying to pick up some caches along the north end of Upper Newport Bay.
I have been over this bridge many times and not given much thought to this particular area where this Earthcache is located. Thanks for “awakening” to this neat part of the bay. A note is on the way with a feebly attempt at filling the logging requirements.

3/20/2008 by rocketgirl35
This was the last cache I was able to do on this quick trip down to SoCal. It was nice to spend a little time in this nature preserve just chillin' and learnin'! TFTC! (436)

3/17/2008 by KChaney56
How many times have I been across that bridge on my roller blades or with my dog. What a wonderful place to geocache and get some exercise. My dog and I love to go down the path by the bridge and hike the lower trail.

3/8/2008 by Me & Bucky

Bucky & I found this one while on Day Four of an Earthcache run around southern California. Started the day in Irvine and cruised up the coast, stopping at beaches and other great spots which highlighted the geology of Coastal California. The day ended with, of all things, a green flash at sundown just north of Malibu while driving up the coast!

Lots of people were using the trail and bridge this morning, and I had to keep on my guard so as to not get run over.

Thanks for another great Earthcache!!