Earth Crust Is VERY Thin

This Limits Oil Sources

(crust is far less than 1% of earth's volume)

(and sedimentary rock is less that 10% of the crust --- so
far less than 0.1% of earth's volume is potentially oil-and-gas-bearing)

(2012 May blog post)

Note: Some more links and further information may be added in the future.

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Introduction :

In the day-to-day news about oil and gas and gasoline (prices and resources), it seems that no one is giving a perspective on where the oil and gas comes from --- in particular, Mother Earth's limits to oil and gas resources.

Our fossil fuels are coming from a very thin crust of the earth --- and the liquid fuels are being used at an alarming rate by an exploding world population.

Back in the 1960's, when I was growing up and going to college in Texas, I worked for several summers in the oil exploration side of the oil industry --- one summer for Shell Oil Company and several summers for an oil exploration company that did seismic exploration for the big oil producers like Texaco. Seismic oil exploration involved setting off explosive charges in the ground and recording the reflected energy waves that came back from deep layers of rock.

The seismic recordings, at that time, were ink 'squiggles' on long strips of paper. I was working as a 'doodle-bugger' in an office --- calculating 'move-out' corrections to the data measured from those squiggles, so that estimates of the depth of various rock layers, at points below the explosive charges, could be used to draw contour maps of the subsurface rock layers.

The first summer that I worked for Shell Oil Company, I was assigned to a petroleum engineer who was studying seismic data that was being used to look at a possible oil-bearing structure about 15,000 feet deep --- about 3 miles down --- near the igneous rock below the sedimentary rock of this 'slightly humped' structure.

Actually, the structure had been drilled once already. We were looking at the seismic data again to see if the structure extended far enough to risk drilling another well nearby. (It didn't extend enough to be worth the risk/expenditure.)

Note that oil and gas are laid down in sedimentary rock --- NOT in ultra-hard rock like the metamorphic rock (such as marble and quartzite) and igneous rock (such as granite and basalt) that lie below sedimentary rock or that jut out from the earth --- in mountain ranges and canyons like the Rocky Mountains and the Allegheny Mountains and the Grand Canyon.

In fact, igneous and metamorphic rock make up 90 to 95 percent of the top 16 kilometers (10 miles) of the earth's crust. So sedimentary rock makes up less than 10% of the crust.

It is very rare that sedimentary rock structures extend more than 4 or 5 miles deep. One runs into metamorphic and igneous rock below the sedimentary rock, and there is no oil or gas in metamorphic and igneous rock.

So even at that time, when I worked summers for oil companies, more than 40 years ago, in the mid-1960's, exploration for oil, on land, in Texas, was reaching the limits of the depth of sedimentary rock structures. In other words, most of the shallow, 'easy' oil (and gas) had been found back in 1961-1964.

So it is not surprising that about 50 years later, oil and gas prices are starting to take off. It is much, much more expensive to recover oil from drilling offshore than it is to drill on land. The deep sea rigs are extremely expensive to build --- and rent.

This graph shows that oil prices jumped from about $25
per barrel in early 2003 to over $55 in early 2005 ---
in other words, during the presidency of George W. Bush.
And prices were around $100 a few years later,
at the end of his second term.

Note: The shape of this graph is reminiscent of the world population graph above.
It is probably the case that the steep growth in population will keep oil prices climbing.

Some perspective on the crust of the earth :

Note that the sedimentary part of the crust of the earth is seldom more than 4 miles deep and the radius of the earth is about 4,000 miles. So if you drew a circle of 1 inch radius to represent the earth. The sedimetary crust would be about 0.001 (one thousandth) of an inch thick --- thinner than the thin black line of the circle below.

The diagram below offers another view --- in which the thickness of the crust is exaggerated, to give it some thickness, between two circles, in the drawing.

Time after time in drawings of the internals of the earth, the authors of the drawings have to exaggerate the thickness of the crust --- so that the crust shows up as more than a very thin line in the drawing. The diagram below offers another example of this.

The two drawings above indicate that the radius of the earth is 6,371 kilometers. The following drawing indicates that this is about 4,000 miles (800 + 1400 +1800).

The following diagram of a typical cross-section of the earth's crust indicates that the crust is often mountainous --- and that the mantle below the crust is made up of very hot rock (unsuited to oil deposits), with molten rock below that.

The following diagram indicates that a rather small portion of the crust of the earth is sedimentary rock. A large portion of the crust is made up of metamorphic and igneous and basaltic (extruded igneous) rock.

Here is another diagram showing that the sedimentary (potentially oil-bearing) rock is a relatively small part of the crust. And when you consider that oil pockets make up far less than 10% of the volume of the sedimentary rock, you can see that the volume of oil on earth is a teeny-tiny fraction (much less than one-hundredth of one percent) of the volume of the earth.

The following diagram indicates that the 'mantle' layer, below the crust, is very hot 'plastic' rock composed largely of iron, magnesium, aluminum, silicon, and oxygen --- and the 'core' is liquid iron and sulfur --- and the 'inner core' is solid iron. No oil in those layers --- which are more than 99% of the volume of the earth.

Click on the still image below of the convection (movement) of the hot, plastic rock in the mantle --- to see a movie of the convection. (There is no oil in this turbulent molten rock.)


Here is a diagram that indicates that the crust of the earth is less than half of one percent of the earth. And since sedimentary (potentially oil-bearing) rock is less than 10% of the crust (as was mentioned above), the potentially oil-bearing rock is less than 0.05% of the earth --- less than one-tenth of one percent.

Here is a diagram that indicates that Iceland was formed from a plume of molten rock --- so you are not likely to find any oil in Iceland. And since many areas of the earth (including under the sea) are quite mountainous, there are a limited number of land areas in the crust that can harbor oil.

Note that the following curves of historical and projected oil and natural gas production indicate that U.S. production peaked around 1972 and that production in the Middle East peaked before 2000. Russia peaked before 1990 and all regions of the earth peaked before 2010.

This figure --- together with knowing the limited volume of sedimetary rock in the earth's crust, the limited number of pockets of oil in that sedimentary rock, and the explosive growth in the human population of the earth --- indicates that even if the U.S. made some big oil discoveries, those discoveries would be a small part of the world total and would be quickly consumed.

Yes folks, in the space of a couple of hundred years, the human race will use up the liquid fossil fuels that it took Mother Nature millions of years to lay down and convert into liquid burnable energy.

Even if you are a rigid 'creationist' who believes that
the earth is only 6,000 years old, this diagram indicates
that our oil consumption days are just a 'blip' in a
time scale depicting the age of the earth.

Summary and Conclusion :

A combination of

  • an exploding world (human) population (sorry, other mammals), and
  • the falling off of oil and gas production on a world-wide basis

is going to lead to ever-increasing energy costs in the coming years.

It is important that the U.S. quit shilly-shallying around and start developing alternative energy sources --- especially relatively clean and relatively interminable energy sources such as wind (and ocean waves), solar, and geothermal.

The amount of sunlight falling on the earth every minute exceeds the world's energy needs by far. In fact, there are grand plans to tap into 'concentrated' solar energy in North Africa and the Middle East to supply that whole region and Europe with energy --- augmented by wind, hydro, solar photovoltaic, biomass, and geothermal --- as indicated in the following diagram.

The technology to generate energy from wind is here already and proven in many places --- such as Europe and the Canary Islands --- and China is coming on as well.

There are even studies that have shown that the energy in the earth's ocean waves far exceeds human energy needs.

The still images (and movie) above, concerning the internals of the earth, indicate that there is a tremendous amount of heat energy trapped beneath the very thin crust of the earth. The amount of geothermal energy, that it should be possible to develop, dwarfs the amount of energy that was laid down and chemically converted over millions of years, into the form of 'fossil fuels' --- oil, gas, and coal.

Some of the development activities that the U.S. needs to start, such as building an expanded electrical grid, are costly beyond any private partnership's willingness to fund such an endeavor. In the past, the U.S. government has stepped up when private investors could not or would not do the job --- with such examples as the Hoover Dam (controversial), rural electrification (controversial), and the national highway system (controversial).

I should mention that Congress, back around the 1960's, gave nuclear power plants a free pass --- indemnity from lawsuits from nuclear plant explosions. I guess that was easy because it did not cost anything --- yet. Wait until we have our Fukushima --- say, when earth is hit by a large meteorite that sets off a chain of earthquakes that damage some of the 130 nuclear plants in the U.S.

If Congress can give the nuclear power plant industry and their extremely-dirty (as in radiation that sticks around for over a hundred years) power plants special favors, they surely should be able to bring themselves to 'do the right thing' and get started on an electrical grid that will serve wind, solar, biomass, and geothermal.

It is time to get started. There is little doubt that the expanded grid is needed --- for example, in the high wind areas such as north Texas, eastern New Mexico, Oklahoma, Kansas, Nebraska, Colorado, the Dakotas, Montana, Wyoming, and Idaho --- as indicated in the following wind resources map. Also certain coastal areas have wind resources that will need additions to the national electrical grid. Build out the grid and the investors will come.

Let's quit the political wrangling and get started. It's going to take a lot of planning and execution by the technologists.

The U.S. needs to get started developing relatively clean
and relatively interminable sources of energy --- to replace
liquid energy like oil and gasoline --- and very dirty energy like coal.

One possibility, besides wind and solar and ocean waves, is
geothermal. This map of geothermally active areas in the U.S.
indicate that the western U.S. (Nevada, Utah, California, Arizona,
New Mexico, Colorado, Oregon, Idaho, Wyoming, Montana)
are promising areas of development --- many potential sites
being far from scenic areas and nature preserves.

Unfortunately, unlike wind and solar and ocean waves, bringing
heat up out of the crust and mantle will add to the warming
of the atmosphere and probably do almost as much global warming
as 'fossil fuels' --- but at least it's cleaner --- and maybe
tapping geothermal energy sources can be used to reduce
volcanic eruptions, using the energy before it erupts from volcanos.

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Posted on 2012 May 09. Changed page format slightly 2013 Apr 26.