Weight of Giant Rock in CA
The Rock Weight: The Giant Rock is on the left. You can see a woman in black standing next to the split piece on the ground. Photo credit: John Haven
"To calculate the weight of the Giant Rock, you need to figure out how many cubic feet of rock it is."
What does the Giant Rock weigh?
The Giant Rock in Landers, CA weighs tens of thousands of tons. I provide a method to calculate the weight below.
The rock weight, that's the burning question.
My ham radio buddy, John Haven - KC1AAG, emailed me a fascinating photo of a massive boulder while he was on vacation in southern California.
It's a photo of the Giant Rock in Landers, CA.
I decided to share this photo with John's permission with my newsletter subscribers and have a fun game.
One of my questions was, "How much does this thing weigh in tons?".
While some websites out there have numbers, I decided that I'd run the numbers myself and see what I come up with.
How Do You Calculate the Weight of the Giant Rock?
To calculate the weight of the Giant Rock, you need to figure out how many cubic feet of rock it is.
It's not easy to calculate because the boulder is rounded. If it were a nice cube where you can easily calculate the volume of rock, it would be very easy to get close to its weight.
Are There Websites That Have Clues to Its Weight?
There are some great websites that have different photos that offer up some clues to help get us close.
One of the pages I discovered was produced by Barbara LaGrange.
On this page, you'll see some excellent photos taken by Frank Rodrigue. Invoking the Fair Use Doctrine, I've reproduced a few of Frank's photos to help show you how I calculated the weight of the Giant Rock in Landers, CA.
What are the Giant Rock Facts?
- Giant Rock is solid granite.
- Numerous websites say that the base of the rock takes up 5,800 square feet.
- Almost all the websites agree the height of the rock is 70 feet - seven stories.
- The specific gravity of granite ranges between 2.6 and 2.7. Do the math and you'll see that the average weight per cubic foot of granite is about 165 pounds.
Now, let's look at two of Frank's photos.
This is a side view of Giant Rock. Photo credit and (C): Frank Rodrigue
In this great side view of Giant Rock, you see a wonderful profile shot.
While it's not a perfect way to estimate because of the angles involved, etc., You can use a ruler to determine the scale of the rock. When I did this I determined in this photo each inch represented just under 30 feet. So let's round to 30 feet.
If you then take the ruler and get a measurement left to right at the base extending partially into the shadow, you get 2 inches. That means the base of the Giant Rock below the graffiti is about 60 feet.
Divide 5800 by 60 and you get 96.66 feet. Let's go look at a second photo Frank took to see if the measurement of the base of the Giant Rock is close to that.
Here's a photo of Giant Rock taken at 90 degrees to the photo above. Photo credit and (C): Frank Rodrigue
Well, it's not perfect but it's somewhat close! I get 2 and 3/4 inches! So that checks out that the 5800 square feet area of the base is accurate. Realize that Frank may have had a zoom lens on his camera, he could have been a different distance away from the rock than he was in the first photo, etc. So let's just go with the side-to-side measurement in this photo of about 85 feet.
Is There a Clue as to The Giant Rock's Volume?
This photo just above also provides a clue as to the volume. Note how the left half of the top is not equal to the right half. We'll have to reduce our guesstimate to account for this. However, the angle of the photo could be deceiving, so I could be way off here. I don't know for a fact Frank was at 90 degrees to his first photo.
I took Frank's first photo and did an overlay of a rectangle to help us in my guesstimation. Look at this:
I've added a red rectangle to help us in guesstimating the volume. Photo credit and (C): Frank Rodrigue
You can see how by drawing a rectangle over the Giant Rock we can start to try to get a decent guess as to its volume.
See the triangle created by the clouds in the sky? That area is roughly the size of the amount of rock to the left that's not in the red box. There may be more rock on the left that can fit in the empty triangle.
To get a volume of a cube or other rectilinear 3D shape you multiply height X width X depth.
So, we need to do this: 70 (tall) X 60 (wide at base) X 85 (approximate depth) = 357,000 cubic feet.
Now we multiply 357,000 cubic feet X 165 pounds per cubic foot.
That equals 58,905,000 pounds.
Divide that by 2,000 to get 29,452.5 tons.
Remember we had to subtract some volume because of the odd shape in the one side view.
So I'll go on record saying the weight of the Giant Rock is somewhere between 25,000 and 30,000 tons.
How Can the Volume of the Giant Rock Be Calculated Accurately?
You need a giant 3D laser scanner to accurately calculate the volume of the Giant Rock.
There are sophisticated laser devices that can scan the Giant Rock and determine it's volume within a very close margin. But I doubt anyone will haul that out to the middle of the desert for fun and games.
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