Wednesday, October 23, 2013

Rivers Appearing Out of Nowhere: McArthur-Burney Falls State Park

Note: Sorry for the odd character of the photos. My hike was at dusk, and lighting was difficult!

There's no doubt that McArthur-Burney Falls are absolutely spectacular, almost otherworldly. Burney Creek spills over a high ledge of basalt and is joined by myriads of whitewater springs bursting out of the cliff below. It falls into a gigantic deep blue pool of water before flowing down to the reservoir a mile or so downstream.
It is cool and moist even in the driest and hottest part of the year, because the springs that feed the fall are practically impervious to seasonal changes. A lot of water passes through the park each day, something like 100 million gallons every 24 hours.

The geology is interesting. The region includes horizontal flows of basaltic rock along with intervening layers of lake sediments and diatomite. The basalt is jointed and broken up and allows water to sink quickly into the ground (surface streams are surprisingly rare in this wet climate). The diatomite and siltstone layers are impermeable and don't allow water to sink deeper into the ground. It is instead forced to flow sideways until it flows out at a spring such as those in the face of McArthur-Burney Falls
What makes the falls more intriguing is the incredible contrast between the river downstream and upstream of the falls. Downstream, Burney Creek has a sizable flow, as seen below.

I decided to check out the river upstream of the falls and headed up the trail. Fall colors were just beginning to make an appearance.
I can now say I spent some time this summer on the Pacific Crest Trail. A whole mile of it, in fact! It runs through McArthur-Burney Falls State Park on the west side of the creek. It was quiet and quite devoid of other hikers on the Sunday evening when I was exploring.
At the upstream end of the park, Burney Creek is AWOL. There is only a dry channel lined with basalt boulders, aspens and willows.

Making my way downstream, I found a spot where the river appears as a series of pools, but at this point it is not yet flowing. The water table is intersecting the channel of the stream and rising to the surface.
Just a bit further downstream, the river has grown, and after a few hundred yards more, it is a large stream that makes the bold leap over the ledge of basalt.
This has been a strange landscape we have been traveling through, an entire shield volcano with no surface water beyond a glacial lake at the summit caldera, and a lava plateau, also with limited water. Yet the climate is wet, and is ultimately the source for much of the water flowing in the Sacramento River.

I headed back to camp. Tomorrow was the last day of the field class, and we were going to pay a visit to Lassen Volcanic National Park!

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