Spring Fed Burney Falls - CA - Places of Geologic Significance on Waymarking.com

Burney Falls is an excellent example of a rare spring fed water fall which is the primary point of interest in McArthur-Burney Falls Memorial State Park.
Burney Falls is a complex spring fed waterfall system which has migrated upstream by undercutting the sediment beneath a thick lava flow. Burney Creek is fed by springs a short distance upstream from the falls resulting be stable stream flows over the falls year round. The primary part of the waterfall are two channels of the creek which plunge 129 feet into a large pool. The falls appear much wider because from the base the lava springs issue spilling water over a wide area just behind the primary falls.

Text of sign at viewpoint.
Roaring Falls and Trickling Streams
The roaring cataracts that plunge over the cliff and the dozens of tiny falls that seep from its face are all fed by water that originated as snow on and around Burney Mountain. As the snow melts, it seeps through the soil. The water moves through the earth into an underground network of ancient river channels. It flows through these channels until a large portion is forced to the surface less than a mile upstream of the falls.
Labels on diagram on sign.
a - Much of the water that feeds the reservoir originates in the winter snows on Burney Mountain, 15 miles upstream.
b - Melting snow seeps through cracks in the basalt, it forms a reservoir that flows underground throug layers of porous and fragmented rock.
c - About 3/4 of a mile above the falls, part of the reservoir is forced to the surface. In the summer this is the only water in upper Burney Creek and the sole source of Burney Falls.
d - The rest of the reservoir continues to flow below the ground on top of a solid layer of well-cemented gravels that lie beneath the fragmented rock. The sheets of water that stream from the cliff face on both sides of the main falls show you where the two layers meet.


Text of brochure: Burney Falls. . .One of a Kind - A brief Geology of Burney Falls.
Waterfalls are rare geologic forms, and Burney Falls is rare among waterfalls because it is fed from both a stream going “over the rim” and from a line of springs flowing out of the rock part way down the fall’s near-vertical cliff-face. Few sites in the world have this extraordinary combination of falling water issuing from two distinctly different levels.
The Geologic Setting Of Burney Falls
Burney Falls is 129 feet high from its brink to the pool below. Beneath the water’s surface under the two main falls, there is an immersed “plunge pool,” 18 to 24 feet deep, where boulders churned by turbulent water are eroding away the rock under the cliff, causing portions of the steep rock wall to be undercut and occasionally collapse.
As you look at the face of Burney Falls, you can see two distinct rock units, a higher thick sequence of dark lava flows (called the Burney Basalt) comprising the upper part of the cliff face and a somewhat denser and smoother mass of tilted older volcanic rock layers making up the lower part of the cliff. The main waterfall pours over the top of the Burney Basalt, and a prominent line of springs breaks out across the waterfall’s face emerging from the “contact” between the two rock units (actually, from the base of the Burney Basalt flows).
At some time in the distant past, the surface defined by the spring line in the face of the Falls marked the “top of the landscape” (that is, it was the topographic surface). As today, it had the same two hills, one east of the Falls (across the highway) and one west of the Falls with a valley in between. The Burney Basalt lavas had not yet been erupted to flow from their sources many miles to the south into what is now the Burney Creek area.
When the Burney Basalt did invade this region (between about 1.8 million and one million years ago), it covered the older land surface with several flows totaling about 90 feet in thickness at the present site of the Falls. The lava buried the old valley floor between the two hills, and then continued down the valley to where Lake Britton is now, temporarily damming the ancestral Pit River. The lava also partially covered old lake sediments in this region. These lake sediments (from about 2 to 10 million years old) have been buried and turned into rocks called “diatomite;” they can be seen as white chalky-textured outcrops on Lake Britton’s shores and in roadcuts along Highways 89 and 299.
The Supply of Water to Burney Falls
The Burney Basalt lava flows covered the older local stream valleys and forced a new drainage pattern to form. Rain and winter snow-melt could now sink easily into and through the fresh, porous basalt flows and accumulate beneath the new land surface as groundwater.
It is common for water to seep into young lava flows because the cooled rocks are highly fractured and very permeable in many zones with innumerable pores and vesicles (small cavities formed by expanding gases). The pore spaces for water can make up as much as 10 percent of the rock volume, but 1 or 2 percent is more common. Groundwater can accumulate into huge volumes, and slowly work its way through the rock “downhill” beneath the surface, seeking outlets wherever this underground water intersects the land surface (typically this is at stream channels or as springs “breaking out of the ground”). In many rock masses, including the Burney Basalt, particular layers are “aquifers,” very saturated and permeable units, collecting and moving the water downslope much more efficiently than the rock strata above or below them.
There are two prominent aquifers within the Burney Basalt in the area of the Falls. The most obvious aquifer -- defined by the line of springs half way down the Falls -- is right at the base of these Burney Basalt lava flows, where these flows buried the older valley. The old volcanic and sedimentary rocks below the Burney Basalt are not very permeable and allow only the slow infiltration of water; this forces the groundwater at the bottom of the Burney Basalt to drain along this rock contact surface. The water finally bursts forth into daylight as the magnificent line of spring part way down the face of the waterfall’s cliff. These springs flow all year long.
The second aquifer, which also flows all year, appears to be a very porous lava layer (or layers) within the Burney Basalt flows, about 40 to 50 feet above the first aquifer. The top of this second water saturation zone outcrops in Burney Creek 3/4 of a mile upstream from the Falls as Headwater Springs, where it profusely discharges water into the channel bottom at numerous places from there downstream. The surface channel of Burney Creek then carries this water over the rim of the Burney Basalt as the main waterfall.
From winter through the early summer, the main over-the-rim waterfall also receives flow from rainfal and snow melt, but during late summer and fall, Burney Creek is typically a slow moving or often dry channel for many miles above Headwater Springs.
The Future of Burney Falls
What does the future hold for Burney Falls, as it slowly erodes its way up the canyon from its present site? It probably started its “waterfall life” three miles downstream from its present location, near the mouth of Clark Creek (at the edge of the Burney Basalt, near where Lake Britton dam is now). Eroding upstream at what seems like a snail’s pace of only 1.20th to 1/10th inch per year (on average), it has reached its present location. Assuming this same rate of retreat, te Falls will have moved up-valley another 3/4 mile (where the higher of the two aquifers outcrops) in another 500,000 to one million years or so.
From that time on, the waterfall will take on a quite different look. There will be no “over the rim” waterfall in the dry months, but both water-bearing aquifers will gush out as two lines of springs across the steep rock face of Burney Falls.

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