Why is 70% of Earth's sial missing?

The Earth's crust is made of two layers called
sima and sial. Sima is the lower and denser layer.
It is 5 to 10 km thick and covers the entire surface
of the Earth. Sial is 20-70 km thick and covers only
30% of the Earth's surface; this is the elevated
part of the Earth's surface called continents. The
remaining 70% of the Earth's surface is covered with
oceans. None of the existing theories explain how the
sial was selectively scooped up from 70% of the Earth's
surface and deposited on the proto-Moon.

"Andrew Nowicki" wrote in message ...
The Earth's crust is made of two layers called
sima and sial. Sima is the lower and denser layer.
It is 5 to 10 km thick and covers the entire surface
of the Earth. Sial is 20-70 km thick and covers only
30% of the Earth's surface; this is the elevated
part of the Earth's surface called continents. The
remaining 70% of the Earth's surface is covered with
oceans. None of the existing theories explain how the
sial was selectively scooped up from 70% of the Earth's
surface and deposited on the proto-Moon.

Sial is the top layer and would be expected to be the source
of much of the material ejected by the mars-sized impactor
that created the Moon. The 70% of the Earth's surface
covered by ocean is largely areas produced by spreading
zones where magma is welling up.

So what's the problem?

Andrew Nowicki wrote:

The Earth's crust is made of two layers called
sima and sial. Sima is the lower and denser layer.
It is 5 to 10 km thick and covers the entire surface
of the Earth. Sial is 20-70 km thick and covers only
30% of the Earth's surface; this is the elevated
part of the Earth's surface called continents. The
remaining 70% of the Earth's surface is covered with
oceans. None of the existing theories explain how the
sial was selectively scooped up from 70% of the Earth's
surface and deposited on the proto-Moon.

First, for anyone else reading this, "sima" refers to rock
rich in (si)lica and (ma)gnesium, while "sial" refers to rock
rich in (si)lica and (al)uminum. Moon rock more closely
resembles the lighter sial than the heavier sima.

I have no idea how Earth's crust was arranged before the
impact which formed the Moon. Maybe it was already
separated into sima and sial, maybe it wasn't. Maybe there
were continents and oceans, maybe there weren't. In any
case, the material that got scooped up all came from one
part of the Earth-- not likely the area where the Pacific Ocean
is now, but I can't say it wasn't. The material was heated to
the point that much or most of it vaporized. The gases that
were heavy enough not to be blown away by solar wind were
incorporated throughout the body of the Moon.

It seems pretty likely that the rock closest to the surface
was preferentially scooped up. That would naturally be the
lighter sial.

On the other hand, just because 70% of Earth's surface lacks
continents made of sial is no indicator that any sial is missing.
Any mantle rock which is exposed at the surface cools to
become part of the crust. That is mostly sima, exposed at
mid-ocean ridges where seafloor spreading takes place. The
spreading pushes the lighter sial around, causing the sial to
pile up into continents. Piling up and erosion are in dynamic
balance, so the continents never get very much higher than
they are now, or very much lower.

-- Jeff, in Minneapolis

On Mar 26, 10:55 pm, Andrew Nowicki wrote:
The Earth's crust is made of two layers called
sima and sial. Sima is the lower and denser layer.
It is 5 to 10 km thick and covers the entire surface
of the Earth. Sial is 20-70 km thick and covers only
30% of the Earth's surface; this is the elevated
part of the Earth's surface called continents. The
remaining 70% of the Earth's surface is covered with
oceans. None of the existing theories explain how the
sial was selectively scooped up from 70% of the Earth's
surface and deposited on the proto-Moon.

Fresh sima (magnesium-iron silicate) and sial
(aluminum silicate, clay) are produced at midocean volcanoes:
http://www.asu.edu/clas/csss/csss/News/life.html
Unlike sima, sial (aluminum silicate, clay) does not
precipitate at the midocean volcanoe (residual negative
charge prevents clumping), but is propelled toward the
continent by the waves. On shore it settles out as
clay, feldspar or anorthosite (lunar highlands).
When Earth's oceans evaporate, clay and mud, which
line portions of the seafloor, will create the appearance
of sial also dominating Earth's crust. John Curtis

Greg Neill wrote:

Sial is the top layer and would be expected to be the source
of much of the material ejected by the mars-sized impactor
that created the Moon. The 70% of the Earth's surface
covered by ocean is largely areas produced by spreading
zones where magma is welling up.

So what's the problem?

1. When a ball-shaped moon collides with a ball-shaped
Earth, the moon cannot scrape 70% of the Earth's surface.
Even a shovel-shaped moon cannot scrape 70% of the Earth's
surface.

2. The oceanic crust is made of sima, not sial.
__________________________________________________ _______

John Curtis wrote:

Fresh sima (magnesium-iron silicate) and sial
(aluminum silicate, clay) are produced at midocean volcanoes:
http://www.asu.edu/clas/csss/csss/News/life.html
Unlike sima, sial (aluminum silicate, clay) does not
precipitate at the midocean volcanoe (residual negative
charge prevents clumping), but is propelled toward the
continent by the waves.

Sial is the material that continents are made of. There is
little sial on the ocean floor. You are saying that sial
bedrock is somehow moved by the waves that are hundreds of
meters above the sial bedrock. How is that possible?

On shore it settles out as clay, feldspar or anorthosite
(lunar highlands). When Earth's oceans evaporate, clay
and mud, which line portions of the seafloor, will create
the appearance of sial also dominating Earth's crust.

Feldspar and anorthosite are NOT sedimentary rocks. They
crystallized from magma long time ago, in the Archean and
Proterozoic eons. Clays make up minuscule part of the
Earth's crust, so they are not worth mentioning. Sial is
sometimes called granitic layer of the crust, because
it is made mostly of granite, which is made mostly of
silica (SiO2 content = 72%).
__________________________________________________ _______

Jeff Root wrote:

Hi Jeff! I was a member of the Minnesota Space Frontier
Society long time ago. Then I wrote the Earth-to-Orbit
Transportation Bibliography; it is posted at:
http://www.islandone.org/LEOBiblio

First, for anyone else reading this, "sima" refers to rock
rich in (si)lica and (ma)gnesium, while "sial" refers to rock
rich in (si)lica and (al)uminum. Moon rock more closely
resembles the lighter sial than the heavier sima.

True. The Moon's crust is very similar to the sial, but
it has more iron than the sial.

I have no idea how Earth's crust was arranged before the
impact which formed the Moon. Maybe it was already
separated into sima and sial, maybe it wasn't. Maybe there
were continents and oceans, maybe there weren't.

The interior of the Earth is very hot now because it is
heated by the radioactive decay. Most of the Earth's crust
is a solid bedrock made from cooled, solidified magma
(igneous rock) rather than something resembling the moon dust.
This fact indicates that the Earth was even hotter in the past
and its surface was liquid. Another good reason for the hot,
liquid surface of the early Earth is that it was made from
smaller parts that collided at high velocity. When a rock from
space falls on the modern Earth, its minimum velocity is the
escape velocity of the Earth (= 11.2 km/s = 6.96 miles per
second). When rocks smash against each other at such velocity
they do not melt; they become plasma.

I believe that the early Earth was so hot that the
lightweight, liquid sial floated on top and solidified as
a layer of uniform thickness. According to Wikipedia:
(http://en.wikipedia.org/wiki/Crust_%28geology%29)
"The Earth has likely always had some form of basaltic oceanic
crust, but there is evidence it has also had continental style
crust for as long as 3.8 to 3.9 billion years."

The "continental style crust" means sial made mostly of
granite. This means that sial is very old.

In any case, the material that got scooped up all came from one
part of the Earth-- not likely the area where the Pacific Ocean
is now, but I can't say it wasn't. The material was heated to
the point that much or most of it vaporized. The gases that
were heavy enough not to be blown away by solar wind were
incorporated throughout the body of the Moon.

True.

It seems pretty likely that the rock closest to the surface
was preferentially scooped up. That would naturally be the
lighter sial.

On the other hand, just because 70% of Earth's surface lacks
continents made of sial is no indicator that any sial is missing.
Any mantle rock which is exposed at the surface cools to
become part of the crust. That is mostly sima, exposed at
mid-ocean ridges where seafloor spreading takes place. The
spreading pushes the lighter sial around, causing the sial to
pile up into continents. Piling up and erosion are in dynamic
balance, so the continents never get very much higher than
they are now, or very much lower.

Good try, but...

The temperature of Earth increases about 36 degrees Fahrenheit
(20 degrees Celsius) for every kilometer (about 0.62 miles) you
go down. Near the center, its thought to be at least 7,000
degrees Fahrenheit (3,870 Celsius). Sial is made mostly of
granite, which is a hard rock made mostly of silica, which is
the main ingredient of glass.

This means that the top 10 kilometers of the sial is made of
hard and rather cool rock. It is too hard and too brittle to
deform under pressure. It is difficult to imagine what could
generate the enormous force needed to break and pile up the
granite into a pile up to 70 km deep. Furthermore, the sial
part of the crust does not look like a messy pile of rocks,
but like a solid, rather uniform layer of bedrock.

It is very difficult to imagine any geological or
astronomical event that could selectively scoop up
sial from 70% of the Earth's surface. I believe that
the most probable event was a sequence of three
collisions:

1. HYPOTHESIS: About 4.5 billion years ago the Kuiper
belt object that is now 2003EL61 collided obliquely with
another, unnamed, large Kuiper belt object. The oblique
impact caused 2003EL61 to spin rapidly and it transformed
its shape from a ball to american football. The
probability that the impact was oblique is low, on the
order of 0.01, because the 2003EL61 is the only large
object in the solar system that spins rapidly and has
american football shape.

2. FACT: The absence of planet in the place where
Ceres asteroid is now is the only exception of the
Titius-Bode Law. HYPOTHESIS: 4.5 billion years ago
there was a bigger asteroid in the place where Ceres
is now. Let us call it Theia and let us call the
unnamed large Kuiper belt object Orpheus. Ceres has
rocky core overlain with icy mantle. Theia had
the same composition as Ceres but it was larger.
Orpheus was made mostly of water ice. It was not
broken into small pieces by the impact with 2003EL61
because the impact was oblique. The impact hurled
Orpheus into a collision path with Theia. When Orpheus
hit Theia, the impact moved Theia toward Jupiter and
melted most of the water ice. The average distance
between 2003EL61 and Ceres is on the order of 5000 Gm
(35 AU). Diameter of Orpheus was probably on the order
of 1000 km. Diameter of Theia is unknown; let us assume
that it was 2000 km. The probability that Orpheus hit
Theia is on the order of 10^-13.

3. HYPOTHESIS: The enormous gravity of Jupiter hurled
Theia toward the Earth. As Theia was moving toward
the Earth, its mantle of liquid water was vaporized by
the sunlight, creating watery atmosphere. Theia became
giant comet. Its rocky core collided with the Moon thus
creating a new, hot Moon. A few hours later Theia's
watery atmosphere collided with the Earth. It ablated
Earth's sial on all sides except the back 30% of the
Earth's surface. Dust particles made from the sial,
the Moon, and the rocky core of Theia were suspended
in the atmosphere. Some of Theia's atmosphere was
captured by the new Moon. The dust settling on the
hot Moon melted and formed the Moon's crust. When the
collision separated Theia's rocky core from its
atmosphere, the atmosphere quickly expanded due to
the heat generated by the collision and due to reduced
gravity (no core). The expansion reduced density of
the atmosphere before the collision with the Earth.
Theia was quickly loosing its volatile atmosphere
after the collision with Orpheus because much of its
elliptic orbit was close to the sun. If it was loosing
its atmosphere at the rate of 0.1 meter per day, it had
to collide with the Earth in about 10,000 years. The
probability that the collision between Earth and Theia
took place within 10,000 years since the collision
between Theia and Orpheus is on the order of 10^-9.

The probability that all these events occurred is
on the order of (0.01)*(10^-13)*(10^-9) = 10^-24.

One percent of stars in our galaxy, called Milky Way,
has Earth-like planets which have liquid water and
thus seem capable of supporting life. This means
that the probability that the Earth has oceans and
continents is on the order of 10^-26.

There are about 100 billion (10^11) stars in our
galaxy and about 7*10^22 stars in the entire visible
universe. The probability that another planet in
the entire visible universe has oceans and continents
is on the order of (10^-26)*(7*10^22) = 7*10^-4;
about one event in one thousand.
__________________________________________________ __

Earth is a unique planet because it has continents.
(see: http://www.spacedaily.com/news/life-01x1.html)

I believe that the missing Earth's sial explains why
the Earth has continents and it may explain the
Fermi paradox.

In the absence of continents there would have been no
advanced forms of life on Earth because the entire
surface of the Earth would have been covered with
oceans and the only source of minerals for the marine
life would have been hydrothermal vents. The vents
cannot support great abundance and diversity of life,
which is necessary for speedy evolution of life.
Marine life of our planet is confined to places that
have abundance of iron, nitrates, phosphates and
silicates. Nearly all of these minerals are
transported from continents by rivers and winds.

If the planet has no continents, it has no land animals
that can make fire, smelt metals, and create
technological civilization. If the planet has no
continents, but it has an ocean, a giant asteroid impact
may create islands, but these islands are eroded by rain
and wind. There is no plate tectonics to counter the
erosion and it takes about one billion years of plant
evolution to produce roots that can prevent soil erosion.

We are lucky to have massive Moon. Earth's obliquity
(the angle between the Earth's equator and the plane
of its orbit) is 23.5 degrees. If the massive Moon
had not existed, the Earth's obliquity would have
varied wildly between 0 and 80 degrees. Such
variation would have caused extreme climatic changes.

We are lucky to have plenty of water. If we had had much
less water, all our flora and fauna would have perished
during a snowball period. Terrestrial life barely survived
during the snowball periods under two kilometers thick
layer of ice (http://en.wikipedia.org/wiki/Snowball_earth).
Evolutionary rates were incredibly slow then.

We are lucky to have plenty of heavy elements (called
metals). According to Wikipedia:
(http://en.wikipedia.org/wiki/Metallicity)
"These youngest stars, including the Sun, therefore have
the highest metal content, and are known as "Population I"
stars. Across the Milky Way, metallicity is higher in the
galactic centre and decreases as one moves outwards."

We are lucky to be far away from the galactic center
and its high concentration of dangerous, exploding stars.

We probably survived cataclysms and close calls that
left no evidence that we can study.

My estimates are not precise but they do not have to be
precise to convey important truth: we are the only
civilization in the visible universe, so SETI is a waste
of time. There is another proof that planets having
continents are extremely ra if they had been common,
extraterrestrial civilizations would have colonized our
galaxy and our planet billions of years ago.
__________________________________________________ ______

My explanation/understanding of plate tectonics of all
terrestrial planets of Earth size except the Earth:

Terrestrial (Earth-like) planets are made of high density
minerals covered with low density sial. The sial abounds in
silicates, so its physical properties are similar to the
properties of ceramics. Ceramics are brittle. Their thermal
conductivity and coefficient of thermal expansion are low.
The dense interior of the terrestrial planets abounds in metals,
so its physical properties are similar to the properties of
metals. Metals are ductile. Their thermal conductivity and
coefficient of thermal expansion are high.

When a terrestrial (Earth-like) planet is young and hot,
its sial surface is liquid. When the planet cools, its sial
solidifies. Sial does not conduct heat well, so it traps the
heat that is generated in the interior by the radioactive decay.
The entire planet warms up and it expands because all its
minerals have positive coefficient of thermal expansion.
The metallic interior expands more than the ceramic sial,
because its coefficient of thermal expansion is higher.
Great tension builds up in the ceramic sial until it shatters
like a glass pane. We call this event an earthquake. Liquid
magma and volcanic ash escape through the cracked sial into
the atmosphere. We call this event a volcanic eruption. When
the magma cools and solidifies, it seals the cracks in the sial
and the next cycle begins.

If the entire surface of a terrestrial planet is covered with
sial, enormous tension builds up in the sial over millions of
years. When the sial shatters, the earthquakes and volcanic
eruptions are enormous. Volcanic ash absorbs sunlight and thus
cools the atmosphere so much that all land animals freeze to
death.

"Andrew Nowicki" wrote in message ...
Greg Neill wrote:

Sial is the top layer and would be expected to be the source
of much of the material ejected by the mars-sized impactor
that created the Moon. The 70% of the Earth's surface
covered by ocean is largely areas produced by spreading
zones where magma is welling up.

So what's the problem?

1. When a ball-shaped moon collides with a ball-shaped
Earth, the moon cannot scrape 70% of the Earth's surface.
Even a shovel-shaped moon cannot scrape 70% of the Earth's
surface.

2. The oceanic crust is made of sima, not sial.

1. It was not hypothesized that a moon collided with the Earth,
but a Mars-sized body.

2. The impact was off-center, but not a "scooping" blow.

Where does your 70% come from?

Greg Neill wrote:

1. It was not hypothesized that a moon collided with the Earth, but a Mars-sized body.

The Mars-sized body was invented to explain the fact that formation of
the Moon requires about twice the amount
of angular momentum that the Earth-Moon system has now. Where is the
rest of this Mars-sized body now?

Where does your 70% come from?

From geology of the Earth.

wrote in message
oups.com...
Greg Neill wrote:

1. It was not hypothesized that a moon collided with the Earth, but a Mars-sized body.

The Mars-sized body was invented to explain the fact that formation of
the Moon requires about twice the amount
of angular momentum that the Earth-Moon system has now. Where is the
rest of this Mars-sized body now?

"Invented", perhaps. Its size was tuned through computer
simulations of the event.

The core of the intruder merged with the Earth's
during the collision. So it's still with us.


Where does your 70% come from?

From geology of the Earth.

Can you show how?

since the entire planet's surface would have been
melted and recycled during and following the impact
that created the Moon, and since the ocean floors
are certainly new material created via upwelling,
I don't see how you have arrived at your figure.

Greg Neill wrote:
Where does your 70% come from?

simple_language wrote:
From geology of the Earth.

Greg Neill wrote:
Can you show how?

Drill rigs were used to make very deep holes in the
Earth crust. granite = sial, basalt = sima

Greg Neill wrote:
since the entire planet's surface would have been melted
and recycled during and following the impact that created
the Moon,...

I agree. If it had happened, a sial/granite layer of uniform
thickness would have covered the entire surface of the Earth.
It is a mystery how this very hard granite rock was removed from
70% of the Earth's surface and piled up on the continents. The
granite rock is not a jumble but solid bedrock, so if it was
transported by some kind of geological force, this force pumped
liquid sial to a height of up to 70 kilometers. I cannot imagine
any geological force that can pump liquid sial to a height of
70 kilometers (maximum thickness of the sial layer).