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

Find more Earthcaches

Additional Hints (There are no hints for this cache)

1/3/2007 by cooperphoto
we are camping at newport dunes, near the south/wide part of the bay, it was interesting to see this side of it. I drove into the parking lot, only to find that street parking was mcuh, much closer... we took a bunch of photos and will post this weekend, thanks terrry, email on its way.

12/25/2006 by shadow101
I had to make an emergency trip to LA on Christmas eve, so after the shouting was over I had nothing to do. So I drove south to first ECs. I literally had never seen this bay before, but I can see why people like it here. Too bad the "urban planners" have to muck it up. TFTC

12/13/2006 by cache_in_pocket
Out caching on my lunch hour break from Jury Duty. I've been on the other side of the bay, so this makes a nice difference. Parked and went for a little walk. Did my reading prior, so I think I knew what I was looking for. Anyway, this is a real nice spot and trailhead. Spotted some waterfowl as well as some students setting up some sort of research. Thanks for another interesting lesson.

12/8/2006 by lorriebird
Earthcaches are my favorite of all cache types. There is only one earthcache near where I live in southwest Florida, so I am always happy to see one within walking distance of my hotel when I am on the road. I saved this one for my last stop today because I wanted it to be my milestone #300th find! I truly enjoyed the geology lesson here, nice work by the owner. My one regret is that I forgot to put my camera in my hiking bag. (The next time I am in town I will add a picture to this log...) Thank you for the hard work and research that go into building earthcaches!

11/26/2006 by GeoMire
Found during biz trip to Cali...
Had some volunteers working in the marsh area... I could hear someone saying, If you see bees... leave them alone. Maybe I'm odd... but you wouldn't really have to tell me that.
TFT...BUZZZZZZZ...C

11/18/2006 by habu!
I came to log a cache for the Quest game, what I got was two hours with my 13 year old in a cool little museum and had a blast! Once again caching takes me places I wouldn't otherwise get to visit.

10/28/2006 by DiverVan
I was on my way to a friends wedding nearby and saw that I had some time to kill - so why not go caching!?!

It's been many years since I had visited the Back Bay and it was nice to visit again. I was able to easily locate the answers to the logging requirements and had a pretty good idea what I was looking for before I got there. I could see, out in the middle of the bay, the dredge fighting the endless battle of keeping the bay clear.

Thanks for a good excuse to walk around this park on a beautiful sunny Saturday afternoon!

10/11/2006 by geoaware
Performed Maintenance

Hi,
As part of the process of EarthCaches returning to geocaching.com, every EarthCache is reviewed to ensure that each EarthCache listing adheres to the new guidelines.

We wanted to inform you that your EarthCache has been reviewed and successfully meets the new guidelines.

Regards.

Geoaware

9/23/2006 by javaa
Explored the upper part of the backbay today. Did quite a bit of walking, visited the interpretive center (check out the snakes in the activity room) and got a couple of caches. Thanks for the interesting geology lesson. Sort of puts things in perspective! Email enroute.

9/16/2006 by GSBJ Family
Out in the area for a Boy Scout event. The views of the Back Bay were gorgeous today. We enjoyed this educational earthcache and its proximity to the interpretive center was a plus too. Thanks for putting this one together.