Mountains,and Measurements

[robohiker]

Does anybody know why people measure mountains from sealevel, and not from the bottom of the ocean?, After all, if the sealevel rises, will the elevation of the mountains change? And what about high tide? Are the mountains elevations always changing due to that? Iquiring robots would like to know.

 

[Jim lombard]

Mauna Loa

Mauna Loa would be 29,855 feet high if you measured it from the mountain's base.

 

[Mark Schaefer]

Or measure from the center of the earth - Mount Chimborazo is the tallest on earth

Another alternative is to measure mountain heights from the center of the earth. Because the earth bulges at the equator and is not a true sphere, the highest mountain using that criteria is Mount Chimborazo in Ecuador. It is over two miles "taller" than Mount Everest.

 

[Rick]

?? Bottom of which ocean??
How do you define bottom?? Flat bottom, average bottom or a deep trench like Mariana's Trench

Early surveyors probably didn't know how deep many areas of the ocean were, nor where the deepest parts were.

Might as well go from something somewhat level -- Wouldn't That be the average surface level of land mass - Could they have just assumed that anything below sea level was below the average surface level of land mass and start counting at zero rather than -10,000?

 

[Puma concolor]

Let's not confuse height with prominence. Whether you use sea-level or the bottom of the ocean as your measuring stick, the highest mountains are still going to be the highest mountains ... just with a different number attached. Prominence is a different ballgame. Many mountains are more prominent than say Everest but if you use the bottom of the ocean as the measuring point, the most prominent mountains in the world would become the ones right near the sea.

 

[Mark Schaefer]

Actually no mountain is more prominent than Everest. The prominence of the highest mountain on a land mass is defined as its height above sea level. The prominence of all other mountains on the land mass are derived from their cols with the higher mountains on that land mass. The purpose of this thread is intentionally humor rather than confusion. But it never hurts to ask the age old question, why?

 

[Puma concolor]

Okay, other Mark S ... ya busted me on a technicality. I was defining prominence in terms of the surrounding terrain, which I now know is basically the wrong way to do it. I should have said there are other mountains taller than Everest (base to summit). It appears I'm the one who is confused.

 

[eddie]

Elevation is measured in MSL "Mean Sea Level" units. Must be some old tried and true method. Most people are OK with this too - don't let it bother you.

 

[Jim lombard]

Worlds largest volcano

Interesting web-link Mark Schaefer, I'm not surprised that Kilimanjaro made it so high on the list as it rises so prominently from the African plain. Sorry, I have Kili on the brain lately with the upcoming trip.

 

[Mohamed Ellozy]

Mean Sea Level -- Some References

Nobody seems to have answered robohiker's excellent question! A couple of good references I have found are:

• Sea Level: Frequently Asked Questions and Answers
  
• Mean Sea Level, GPS, and the Geoid

 

[Grumpy]

Outstanding, informative links, Mohammed. thanks for posting them.

G.

 

[RoySwkr]

Does anybody know why people measure mountains from sealevel, and not from the bottom of the ocean?

As Rick says, there is a very good reason for this - when accurate land surveying began, nobody knew how deep the ocean was (even now, we don't know that precisely) while sea level could be determined more easily.

After all, if the sealevel rises, will the elevation of the mountains change? And what about high tide? Are the mountains elevations always changing due to that?

I don't have a USGS map in front of me, but I believe that if you look on the East Coast maps the measurement is from something like "mean lower low water 1939" so this is a historic base level and will not vary with time. I believe that West Coast maps use a different datum, which may be mean sea level. Perhaps somebody with more ambition can find this info somewhere on mapping.usgs.gov

 

[Holdstrong]

Jon Krakauer had an essay in his excellent compilation, "Eiger Dreams", about this very topic. Explained the actual science of mountain measurement as well as some of the incredibly interesting history behind it.

The essay itself is called "A Mountain Higher than Everest"

 

[Ridgerunner]

Hmmmm

measure from the lowest earth surface to the highest earth surface,makes sense to me!

Everest still grows a bit, according to the most recent surveys. Why wouldn't the lowest earth surface be a'risin or a'sinkin too ?

 

[MichaelJ]

When I worked as a structural engineer, we had two vertical datums. Newer work was done in NAVD '88, about which I know relatively little. However, all the old plans were in NGVD '29, which was the standard vertical datum derived from the mean tide at a bunch of locations, including Commonwealth Pier (the World Trade Center) in Boston.

Just a little tidbit.

 

[Grumpy]

I don't have a USGS map in front of me, but I believe that if you look on the East Coast maps the measurement is from something like "mean lower low water 1939" so this is a historic base level and will not vary with time. I believe that West Coast maps use a different datum, which may be mean sea level. Perhaps somebody with more ambition can find this info somewhere on mapping.usgs.gov

This link will take you to some interesting information about mapping the United States. You’ll have to study some, but it may provide insights to the marvel of topographic maps that accurately depict our mountains.

G.

 

[Jim lombard]

Biggest?

Our very own Frodo has just climbed the world's BIGGEST mountain. That would be Denali, the largest mountain on Earth when measured from base to summit.

Alpine summit do you know the measurements? I always thought Kilimanjaro was considered the worlds largest freestanding mountain:

Composed of three separate volcanoes, massive and complex Kilimanjaro covers an area 60 miles (100 kilometers) long and 40 miles (65 kilometers) wide. Summit at Uhuru point is 19,340 feet rising over 16,000 feet from the plain.

To me Denali is much more impressive because of the setting and the ferocity of the weather. Frodo and his group showed great determination in the face of that challenge and I admire them greatly.