I was playing around with Google Earth (a recent Pick of the Week over on macosxhints) tonight, when I stumbled across the very odd image you see here.
For those of you who have Google Earth, here's a location file that will take you right to the spot. It's the San Luis reservoir, located in California off of highway 152, between Highway 101 and I-5. (I used to drive this road often when making the trek from San Jose to Los Angeles.)
The oddity is--what's with the bottom third of the reservoir? Has it really frozen solid along an arrow-straight line? Has it been converted into salt flats? Some strange cover to prevent the satellites from seeing what's hiding in the lake?
If you zoom in using Google Earth, you can see that the odd fill color runs precisely along the edge of one particular 'piece' of the overall image, so it's clearly just a glitch in the satellite or the software that processes the images. It definitely caught my eye, though.
It seems as if the lake is covered by small waves/ripples created on a windy day. The ripples are reflecting sunlight back towards the camera, causing that bright white color. It just happens that the lake was stitched together with pictures from different days.
You'll see minimal shadows when looking at buildings, cars, and other objects on the bottom third of the lake, implying that the sun is almost directly overhead. The greener side of the lake has shadows that indicate the sun is low in the southeast. The difference in the light angle causes the bright reflection.
I guess the southern part was photographed some time ago in ice age ...
[2]: Sure, CIA is a nasty agency that didn't say you many things including that thing about taking photos of the planet for some ten thousands years now. :-D
I've driven past the San Luis resevoir tons of times when I lived in Northern California. That resevoir is really susceptible to short-term drought which is quite common in California. It's not a salt lake but there are deposits that are left after resevoirs evaporate/drain off. I've seen that particular resevoir drained also completely at times.
So I suspect that the imaging was just taked at two intervals thus resulting in the peculiar image you see there.
By the way, there is never an extended period of time where the thermometer drops below freezing in that part of the country. At least not enough to freeze a lake of that size. The temperature between Modesto and Gilroy (the part of California where the San Luis resevoir is) might drop below freezing for a couple of days only during the overnight period. That might be enough to freeze the top of a cup of water but not a huge resevoir.
Looking at the bottom of the reservoir, past "Lone Oak Bay", and zooming in, it seems like it's either a sunlight reflection (although the bay itself appears more as digital noise) or the salt that PigInZen suggested. The flow of water in the contributing tributary, but salt in the main reservoir makes sense in that context.
PigInZen sounds right to me re: salt flats -- the grey area in the bottom image looks a lot like some other salty areas I've seen in satellite images, and if you look really close, you can see some color differences which would be little variations in the dried up lake bed (different mineral content, yadda yadda yadda).
Not so sure I think it's water -- water is usually dark, or if you do get a nice specular reflection off of the surface, it would be limited to a relatively small area, and would saturate much more than the grey here suggests.
But that's just my humble opinion :).
(P.S. I'm getting a wacky result with the spam question -- "Salem is the capital of which state? does not accept Oregon as the answer. If you see this post, I used 'Salem').
#6: Whoops, you found an error in my file ... hehe, that was a trick question, I guess :). It's now been fixed. I've also added a number of new questions, and modifed some existing ones, just to keep the "humanoid bots" (yes, there are some, more on that in a future post) on their toes.
And if that's salt, I'd be amazed -- that reservoir is huge. The width of the 'salt' is almost five miles, and it extends about 1.8 miles into the lake. Given the harsh break line at the edge of the area, it's clear that whatever it was must have extended further out into the lake at some point; it's not a natural break line.
Also, on the right edge, near the dam, the white stuff clearly covers some human-made objects, which makes even less sense.
I still think it was a glitch of some sort in the image processing. Who knows, though it's fun to speculate.
-rob.
FWIW, I also doubt the salt/mineral deposit theory. There are no "dry surface" patterns, erosion, etc. visible in the light area. Zoom way in and look at the shore/waterline at the seam between the images, and you note that the water level is obviously LOWER on the image with the dark water. (See especially the southwest corner, and the shoreline on the peninsula.) The reservoir was actually quite a bit more full when the "light water" picture was taken. Due to that, and the wave patterns visible when you zoom way in, I'm going to guess it was a combination of sun reflection and odd digital processing that made it look that way.
Zoom in very close and you can see water ripples/waves. The water level was much higher on the day that the southeast section was photographed and the wind was blowing quite steadily and fast. When I angled the view I could clearly see ripples/waves. In the inlet areas runnning east/west, where the walls of the the slopes are up to 100 ft high, the there are no waves and one can clearly see darker strips of what might be algae, indicative of calm water areas.
Why so white for a water reflection? I can only surmise that the satellite might have shot this when clouds were overhead but northwest of the camera view. If you look at the mesas near the edge of the water you can also see that the sun shadow is very shallow, perhaps only a few feet, and pointing to a sun that is to the east. This indicates a winter shot around 10am. Cloud cover is highly possible.
God, I've got to get a life.
Ah, one more proof that it's a water reflection. Go to...
37 02' 48.73" N
121 04' 11.47" W
I'm zoomed in down to 1217 ft (eye altitude) with a tilt. There's a "bump" in the dam wall that juts out into the water. Look at the waves curving to the right around the lower corner of that jut.
Also, most of the white color is coming from reflection from the wave peaks. Look between the waves and it's pretty dark.
A quick glance shows texture on the illuminated or white side as well as sun reflection. The clean line suggests a scan was made only part way across the imaged area when the sun was in position to reflect off of the water.
The rest of the image, with the dark area shows detail on the waters surface that would have been washed out in the glare from the earlier alignment between sun and imaging device.
Couple this with the shadow anaysis previously referred to (by Pcheese) and you have a composite image creating an entertaining but explicable anomaly. Kinda like the face on Mars.
A similar multi-photo thing happens when you view downtown anywhere: One side of the block, the highrises may loom up to the left, the other side up to the right or down. Like viewing an Escher photo.
I don't know to much about that picture but I have pasted it many times, every time I pass by I always see the lake vastly empty... No boats, not fishers, no nothing, not even some brids by the shore line. I do sometimes see a small boat but thats all.I don't know whats up with that lake...
When i went on my google earth, and typed in the same place, there was no white part at the bottom. it said that the pic was taken 10/6/2010, so may there was a glitch on your computer, or it was just an old picture.
I posted this in 2006; Google has obviously updated the image since then :).
-rob.
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