Plate Tectonics
Plate tectonics turn out to be extremely important for a planet to have intelligent life. One of the greatest advances in astronomy has been made in the last few years. This discover is the presence of thousands of planets orbiting nearby stars.
Naturalists have used this discovery to imply there must be numerous Earth-like life-promoting planets nearby. If Earth-like planets are plentiful, it is likely many of them also have life. Some of this life might include intelligent life right at our backdoor.
The idea of nearby intelligent life is promoted by popular science fiction stories such as Star Trek. Story lines include multiple foreign civilizations all competing with each other for local dominance.
But most of the planets discovered so far would be very unlikely to hold advanced life. Many are very large gaseous planets with eccentric orbits around their star. These planets are not at all similar to the Earth. Others are baked by the intense heart associated with their orbits taking them near to their star. Any carbon-base like could not exist under those circumstances.
It turns out planets must have a size similar to the Earth in order to sustain life, and have other characteristics as well. Probably the most important requirement for intelligent life is plate tectonics.
Plate tectonics
It may seem odd that plate tectonics could be so important for the production of intelligent life. This is true for some of the following reasons.
Biodiversity. Plate tectonics promotes high levels of global biodiversity. The major defense against mass extinction is biodiversity.
Stability of Temperature. Plate tectonics is on one of the most important factors in the stabilization of the Earth’s temperature. It does this by recycling carbon dioxide in our atmosphere. It also is important in enabling liquid water to remain on the Earth’s surface for 4 billion years.
Sea Level. Plate tectonics is the dominant force causing changes in sea levels. The sea level is important in the formation of minerals keeping global carbon dioxide stable.
Continents. Plate tectonics is important in the production of land continents. Land formation is where animal life might live and thrive. Without plate tectonics, the Earth would appear as a watery world with only a few isolated volcanic mountains.
Magnetic field. Tectonics make possible our planet’s magnetic field. Without the magnetic field, the Earth would be bombarded by potentially deadly radiation and solar wind.
Origin of Plate Tectonics
Image by Free-Photos from Pixabay
Plate tectonics is the movement of landmasses on the underlying soft mantle. When this idea was first proposed by American geologist Frank Taylor in 1910, it was considered heresy.
Alfred Wegener took up this hypothesis and worked on tectonics from 1912 until his death in 1930. He was able to show how the fit of various continents suggested they were once together. He also demonstrated how similar fossil species were on land masses that became widely separated over time. This similarity in fossil species could only occur if the continents were once together.
Arthur Holes later suggested that the upper mantle might act like a cushion upon which the continents could drift. This cushion is caused by the hot mantle rising to the surface. The mantle either comes out as volcanoes or move parallel to the surface as a cushion. It then cools and drops down toward the Earth’s center to be reheated.
The circulation of molten rock forms the cushion upon which the Earth’s crust moves.
Tectonic Plates and Continental Drift
Evidence from many sources now indicates the theory of continental drive seems correct. All continents are masses of low-density granite rock which rests upon higher density basalt. The low-density rocks ride across the higher density rocks.
The Earth has a radioactive interior that constantly generates great quantities of heat. This heat produced by radioactive decay and other factors rises to the surface creates liquid rock upon which the crust floats.
The plate tectonics with the continental crust average about 100 kilometers in thickness. They rest on oceanic crust and mantle about 50 kilometers thick.
Basalt Rock. The crust underlying the oceans is made primarily of basalt. This is the volcanic rock that makes up the Hawaiian Islands. The volcanic rock arises deep within the earth where it is heated by radioactive decay. When it reaches the surface it enters cracks.
These cracks are formed by the pulling apart of two layers where they come in contact with ocean water. The ocean cools the lava forming basaltic ocean crust. The plates then move further apart and more lava rises to take its place.
Over millions of years, the ocean crust formed from basalt rock gradually moves apart as newer basalt rock gets laid down. As the basalt rock cools, it gets denser and starts traveling down due to its increased density. The downward journey of basalt into the deep mantle is a process called subduction.
Subduction Zones
Subduction zones are linear regions where the oceanic basaltic crust is being driven deep into the Earth. It is near and parallel to these subduction zones where mountains occur. The collision of two plates causes the leading edges to crumble and buckle. The upward movement of hot magma eventually solidifies into granite parallel to the subduction zones.
Most of the world’s volcanoes are located along these subduction zones. Mountain ranges are not found in any other planet in the solar system showing that the Earth is unique.
The continents are less dense than the basalt upon which they float, and can never be sunk into a subduction zone. Continents once formed cannot be destroyed although they can be eroded, split and fragmented. Through time, the volume of the continents on the Earth has gradually increased.
Geologist David Howell in his book Principles of Terrane Analysis estimates that the volume of continents increases by 650 to 1300 cubic kilometers per year.
Tectonic Plate Interactions
Tectonic Plates can interact with each other in three ways:
- bottom of the oceans where two plates spread apart with hot magma filling the space,
- where plates grind side by side such as the San Andreas Fault
- where plates collide at the subduction zones which are associated with volcanoes such as the Cascades and the Aleutian Islands
Plate Tectonics are Important to Life
Most of the Earth’s biodiversity exists on the continents. This relationship has probably existed over hundreds of millions of years. As continents grow, they affect the ability of the earth to reflect heat and light. They also change ocean circulation patterns, and nutrients reaching the oceans.
Plate tectonics affect biodiversity by increasing the habitats where life can live. Mountainous continents, oceans, flat plains, and islands produce a diversity of habitats that can host a diversity of life.
Changes in continent positions affect ocean currents. This could affect temperature, seasonal rainfall patterns, distribution of nutrients and patterns of biological productivity.
The deep-sea is the area on Earth with the least biodiversity. Over two-thirds of all animal life live on land. Biodiversity would be expected to be lower with only one large continent.
Plate Tectonics and Global Temperature
Image by LuisValiente from Pixabay
It turns out that plate tectonics are very important for the maintenance of global temperatures.
Greenhouse gas composition is a complex interaction among the planet’s interior, surface, and atmospheric chemistry.
Plate tectonics recycle mineral and chemical compounds bound up in the planet’s rock layer. With plate tectonics, the interaction of plates, formation of mountain chains, and subduction and volcano formation all lead to a recycling of materials.
Carbon Dioxide
One of the most important of these reactions is the cycling of carbon dioxide. As limestone is subducted deep into the mangle, it changes and releases large amounts of carbon dioxide into the atmosphere leading to global warming.
The burning of large amounts of hydrocarbon fuels can fuel global warming on a planet. As a tectonic planet warms, it becomes more efficient at removing carbon dioxide from the atmosphere.
The basic chemical reaction is,
CaSiO3 (calcium metasilicate) + CO2 = CaCO3 (limestone) + SiO2 (sand).
The weathering of silicates such as mica and feldspar (found within granite) exposes new rocks which can absorb carbon dioxide and form limestone. When weathered, granite can remove large volumes of carbon dioxide from the atmosphere. This will tend to cool the planet.
As the planet cools, weathering will reduce and the carbon dioxide content of the atmosphere will increase.
Plate Tectonics and the Earth’s Magnetic Field
The Sun
The Earth’s magnetic field protects us from harmful ultraviolet light and high energy particles which constantly hit the Earth.
These come from the Sun and deep space sources such as supernovae and star explosions.
Advanced life would be impossible without the planet’s magnetic field.
Iron is the major component of the Earth’s inner core. As the planet spins, it creates currents in the liquid. Heat loss enable convection currents within the iron core. Without plate tectonics, there would not enough heat loss from the core to produce the convective currents needed to generate Earth’s magnetic field.
The magnetic field around the Earth also protects our atmosphere from the solar wind.
Without plate tectonics, there would be no magnetic field and no animal life.
Conclusion
Plate tectonics play at least three crucial roles in the maintenance of animal life on Earth.
- promotes biological diversity by the production of different landmasses.
- enables the temperature stability needed for animal life;
- produces a large magnetic field needed to protect the earth from dangerous ultraviolet light and cosmic rays
- is doubtful planets without plate tectonics could support any advanced life – it is that important.
Planets discovered elsewhere without tectonic plates are unlikely to be suitable for advanced life, even if “earth-like.”
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