The earth is unique in the solar system because of the presence of liquid water at the surface, and its high density core. The earth's atmosphere, also, is uniquely constituted for sustaining life. But evidence for ice and water elsewhere naturally leads to the question, why couldn't the earth's interior also contain an ice layer? The Subcrustal Ice Earth Model (SIEM) is being developed to investigate this possibility.
According to the conventional theory of plate tectonics, water and other materials from the earth's surface are recycled to the deep interior by hypothetical processes of subduction and convection. The driving force for the postuated movements of the plates is mantle convection, a process invoked by Arthur Holmes as a mechanism for continental drift.
The Inner Workings of the Earth by Michael Wysession, from American Scientist, March-April 1995 presents a discussion of current thinking about mechanisms for recycling water and other materials from the earth's surface to the deep interior. According to the theory, some of this water returned to the interior by convection driven processes becomes ejected in volcanic eruptions.
The convection hypothesis comes under critical scrutiny in: Is mantle convection no more than a storm in Arthur Holmes' porridge bowl? This author of this article [presumably Dr. Ken Duckworth, professor of geophysics at the University of Calgary], uses the pseudonym A.H.E.Retic. He tilts against "a concept so powerful that even today it has become a Mantra to be chanted by all should they ever hope to get a grant to study any aspect of the crustal behaviour of the earth". The article identifies several fatal flaws in the standard dogma of mantle convection, and develops some helpful Retic's Rules.
Could the concept of recyling of water from the earth's hydrosphere back into the depths of earth, (needed for the conventional view of an ancient earth, billions of years old) be wrong? Thermodynamics suggests bodies that are heating up degass. The high concentration of radioactive isotopes in rocks could mean the earth is heating up. See The Heat of the Earth.
A 1995 paper by Lars Stixrude, Mineral physics of the mantle from Reviews of Geophysics considers possible mechanisms by which water and volatiles could exist deep in the earth's interior, combined with other minerals. Stixrude notes that 1% by weight water stored in the earth's mantle amounts to 30 hydrospheres.
If the water and volatiles in the earth's interior are primeval, the earth could not be billions of years old!
The New Alchemy by Robert M. Hazen reviews the history of high pressure research.
Deep Waters is a recent article from New Scientist about why abundant water exists in the earth's mantle.
Earth's Interior May Contain Oceans Of Water, Geologist Says
Earth Density inter-active model - Try to figure out the density distribution in the earth, with the correct total mass and moment of inertia.
AK135 Travel Time Tables: A seismic model of the earth's interior.
This chart of seismic velocities shows clear discontinuities exist in the earth's upper mantle near about the 400 km and the 660 km levels. Deep-focus earthquakes are clusted near the discontinuity at 660 km. Some scientists consider these deep earthquakes to be anomalous; conventional earth models assume very high temperatures exsit at those depths, where earthquakes would be less likely to occur; see What is exploding 400 miles beneath our feet?
Information about gravity and magnetic anomalies and their implications for the earth's interior is discussed at: Complexities of the inner earth.
Phase DiagramsThe diagram at right is a phase diagram for water to 200 kbar and 450 degrees C. This is figure 1, p. 2455 from Mishima, O and S. Endo, 1980. Phase relations of ice under pressure. J. Chemical Physics 73(5) 2454-2456.
H2O Phase Diagram for low pressures.
Elastic Properties of Ice VIIThe graph at left shows the variation of the elastic moduli of Ice VII with pressure, calculated from experimental data in: Polian, A. and M. Grimsditch. Brillouin scattering from H2O: Liquid, ice VI, and ice VII. Physical Review B 27(10): 6409-6412, May 1983.
The upper line shows the Bulk Modulus; the lower line is the Shear Modulus.
Seismic Velocities of Ice VIIThe graph at right shows the variation of seismic velocities with pressure in Ice VII, calculated using the data in the previous reference together with more recent published density measurements.
In the convection hypothesis, enormous amounts of heat must also be continuously supplied for the duration of the vents to heat the circulating sea water.
For an introduction to submarine hydrothermal vents, see Deep Sea Hydrothermal Vents by Melanie Summit and the University of Washington School of Oceanography Exploraquarium.
A discussion of the convection mechanism can be found in Hydrothermal processes at mid-ocean ridges by Susan E. Humphris.
Photos and videos of black smokers can be found on the following sites:
|Vents Geology Program|
|Exploring the deep ocean floor: Hot springs and strange creatures|
|VENTS Video Clips|
|VENTS Image Gallery|
|The National Oceanic and Atmospheric Administration's Vents Website|
The rocks of the ocean crust and the earth's interior and hydrothermal emissions are enriched in the primordial helium isotope, 3He. The higher 3He/4He ratio of vent emissions distinguishes them from sea water.
The plume of 3He enriched seawater caused by hydrothermal venting or volcanic activity at the East Pacific Rise was investigated by the Helium and Tritium in the World Ocean Circulation Experiment (WOCE) Pacific Program.
Waters Under the Earth - What ancient scriptures say about the subterranean waters.
The Biosphere Below by Daniel Grossman and Seth Shulman discusses the living microorganisms that thrive kilometers deep in rocks, some called heterotrophs, which feed on decaying plant or other organic material buried in sediments; others called lithotrophs, perhaps the most common, which live off geothermal energy, eating hydrogen present in deep rock formations.
New evidence for long-distance fluid migration within the earth's crust by M. Person and L. Baumgartner cites evidence for fluid movements of hundreds of km.