soficrow:
First, a few words on your PODCats
What can I say? I find myself each time listening to your PODCasts not once, but multiple times...
The style in which they are produced is engaging...thought-provoking...entertaining...haunting...and perhaps most of all...memerable. They are a
surprising blend of art
and science- a combination rarely seen. The elements are skillfully woven in a way that leaves me quite impressed.
Now on to the matter of the substance of your PODCast...
Who knew? I didn't. The thought had simply never occurred to me. How significant
is human impact on the
geology of the planet?
Leaving aside for now the conspiracy implications you raise, I realized that we very often fail to view human environmental impact from a
macro-environmental perspective.
Humans may surpass other natural forces as earth movers
Think of large earth moving projects: highway interchanges, coal mines or Boston's Big Dig. According to Roger LeBaron Hooke, a University of Maine
scientist, such activities have propelled humans into becoming arguably the most potent force in shaping the planet, surpassing rivers, wind and other
natural phenomena. He finds this achievement troubling, and other scientists are taking note...
Hooke has put human earth moving into an historical context. After all, people moved rock to build monuments such as Stonehenge in England and
pyramids in Egypt and the Americas. In the journal Geology in 2000, Hooke estimated that over the last 5,000 years of human history, the total amount
of soil and rock moved by people would be enough to build a mountain range about 13,000 feet high, 25 miles wide and 62 miles long.
In the last century, powerful technologies have enabled people to accelerate this process. At current rates, the size of that metaphorical mountain
range could double in the next 100 years, he wrote. "One might ask how long such rates of increase can be sustained and whether it will be rational
behavior or catastrophe that brings them to an end"...
Among the environmental problems linked to these activities are acid mine drainage and river sedimentation. Mountaintop removal, a technique for strip
mining coal in the Appalachian coal belt, results in the destruction of river valleys, he adds.
This article certainly puts into perspective the scale of the issue, but it is still somewhat hard to visualize.
That had me thinking about Valhall's post:
Originally posted by Valhall
1. Oil extraction does not cause a big subterranean cavern. By and large oil is extracted from the pores of the rock, much like drawing fluid from
the pores of a sponge. Though there may be a few oil "pools" in which there are actually significant voids filled with oil, it is extremely rare
and does not constitute the majority of oil production. Concerning any "pools" or voids that are created by these rare cases...The earth is about
8000 miles across. Pretending we could create a void with the typical oil reservoir, we're talking about a hole around 1000 ft high and maybe 3000
ft in radius in all directions.
That's equivalent to a pore on your left cheek. And that's not what happens day in and day out.
2. A chamber tends to dampen amplitude. So if you wanted to formulate that the
EVIL oil companies are causing voids in the earth...you'd be
working against an amplification of waves since any significant void would cause a diminishing of the amplitude. (Hence the reason dampening chambers
are used in pressure pulsing situations - to dampen the amplitude of the pulse.)
If you think about the issue on a global basis- all of the drilling (on shore and off), all of the mining, and all of the development- it does tend to
raise the question of whether in the aggregate those activities make a difference? Let's remember that these activities tend to be heavily clustered
in a variety of places across the planet.
Now, returning to Valhall's post, she points out that in the case of drilling, most often what is left behind is a porous material, as opposed to a
cavernous void. However, I also assume that when a well runs dry, or drilling is no longer productive, that the porous material that remains is either
dehydrated or geologically filled with water. That would certainly change the properties of these fields to one characteristically different in
a geological sense from the fields they were when filled with oil or natural gas.
I could not help but visualize a kind of 'swiss cheese' effect we might potentially be creating. Consider for a moment the items below:
external image
All of the regions that have produced oil and natural gas in the South Central United States
and...
Interactive Gulf of Mexico Oil Rig Map
It's hard to imagine that all of that activity would not have at least
some impact on the geological characteristics of those areas. Is that
enough to change an area's behavior during seismic activity? I don't know...but, I suspect it.
Consider also the following:
MELT data sheds new and surprising light on birth of oceanic plates
PROVIDENCE, R.I. -- The East Pacific Rise, a vast volcanic mountain range submerged in the eastern Pacific Ocean, is one of the fastest seafloor
factories on the planet. Here, along a rocky spine that runs about 1,000 miles west of South America, oceanic crust is created from magma bubbling up
from deep within Earth's interior.
Forces that shape these young oceanic plates have come into clearer focus through research conducted by scientists at the Woods Hole Oceanographic
Institution, Brown University and the Japan Agency for Marine-Earth Science and Technology.
The research represents the first time that seismic and electromagnetic data were analyzed in tandem from 1995 Mantle Electromagnetic and Tomography,
or MELT, Experiment. MELT employed 51 ocean-bottom seismometers and 30 magnetotelluric receivers two miles under the sea to measure sound waves and
magnetic fields along the East Pacific Rise, making it one of the largest marine geophysical experiments ever conducted.
In a paper published in Nature, the team notes that in
rock down to a depth of about 60 kilometers below the ocean floor, electrical currents
conduct poorly and sound waves travel rapidly. Deeper down, beyond 60 kilometers, there is a dramatic increase in electrical conductivity, and sound
waves travel at their slowest.
A switch in seismic and electrical properties with depth was expected. Researchers were surprised, however, at how close to the East Pacific Rise this
structure develops and how little it changes with increasing distance from the rise.
Brown marine geophysicist Donald Forsyth said the team, led by Robert Evans from the Woods Hole Oceanographic Institution, has a theory about the
cause of the sudden compositional changes at 60 kilometers: dehydration.
As magma migrates to the surface to form crust at the rise, it leaves behind a dry, residual layer about 60 kilometers thick. This change from "dry"
surface rock to "damp" rock below it increases electrical conductivity and slows seismic velocity, the researchers write.
Here is what they did not expect: These changes occur, the team found, less than 100 kilometers away from the highest point on the ridge. And the
seismic and electrical measurements remained nearly constant at least about 500 kilometers away from the crest.
Separating seafloor guides magma up to mid-ocean ridges such as the East Pacific Rise, where the molten rock erupts, fans out along the ocean floor
and cools to form new crust. Cooling allows sound waves and electrical currents to travel faster. But scientists thought this cooling – and the
resulting changes in the rock – would be gradual.
"About two-thirds of the Earth's surface is oceanic crust – and it is all formed at ridges," Forsyth said. "So this work helps us better
understand the basic processes of how this crust is formed."
In what light does this place my theoretical 'swiss cheese' and its behavior with regard to seismic activity?
Even if our current level of drilling, mining and development activity is not enough to make a difference now, then how much is? Do we know?
Shouldn't we know?
I wonder...
Or as soficrow would say..."ya gotta get some informaaaaattttiiiiioooooooonnnnnnnnnnn".
[edit on 15-10-2005 by loam]
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