Plate tectonics 3.0- A unique shapeshifting ⋆ TheScientificRevelation
Hello, folks. You must be thinking why am I writing so many blog posts on plate tectonics. The truth is when I started to research more around this topic it had blown my mind. I can’t even emphasize the fact that how much plate tectonics had influenced everything around us. It is literally the deal for biology as we know and ecosystems as we see. The majestic structure we see around had resulted from tectonic movements and it is mind-blowing. It is the reason we are here, here is here and everything on here is here. In this blog post on Plate tectonics 3.0- A unique shapeshifting, I will take you to the phenomenal geology of natural disasters and plate tectonics on other worlds.
I can’t even emphasize the fact that how much plate tectonics had influenced everything around us. It is literally the deal for biology as we know and ecosystems as we see. It is the reason we are here, here is here and everything on here is here. It’s important to understand if tectonism is influencing life on earth so how much it is affecting other worlds. Along with it, we will see the deadliest disasters are just an extension of plate movements.
It’s important to understand if tectonism is influencing life on earth so how much it is affecting other worlds. Along with it, we will see the deadliest disasters are just an extension of plate movements.
Plate tectonics and natural disasters
Every scale and size of geologic activity has its connection to tectonic movements. Our earth had shaped and still getting shaped due to tectonic plates.
Our relation with volcanoes is very old, as old as the formation of the earth. They have started doing their magic when earth first assembled out of the remains of the solar nebula. Volcanoes have been attributed from the arrival of the ice ages to extinction events. 80% of the land of the continents have been made out of volcanic eruptions only. The earth releases its heat and energy through volcanic eruptions only. The importance of volcanoes is immense. The volcanoes that have created the Siberian trap( layers of volcanic lavas) considered being behind the great dying. They release gases into the atmosphere and maintain the greenhouse effect without which the earth will freeze. Indeed an important Mechanism.
The formation of Volcanoes
We have two ways by which volcanoes form. Firstly along the subduction zones that lie at the edges of continents. Subduction zones are places where one tectonic plate is driven underneath another plate. The heavier plate which goes underneath starts to melt due to heat and pressure. Plate forms when volcanic lava cools so when plates melt they naturally turn into magma. The melting plate also has water in it as well as water also sips from the ocean basin. This water after turning into gas lower the pressure from above the plate and increase the pressure of newly created magma. This pressure needs to escape and the above layer can not hole it for long. It erupts and when it does volcanic mountains are created.
All subduction zones have volcanic mountain chains and 70% of them are in the ring of fire, chain of subduction zones encircling the pacific ocean.
Secondly, volcanoes are created by magma plumes. We all know that the earth is full of fissures and cracks. Sometimes magma from the mantle travels all the way up and reach just below the plates. Through the fissures on a plate, this magma finds an opening and erupts. This is how volcanic islands of Hawai have formed. Here, again is a twist of tectonic movements. This magma plume remains stable but because plates over it move slowly over time chain of islands forms. The older volcanoes erode because they have no magma chamber to feed them.
The plates move on the top of the Asthenosphere which is the uppermost part of the mantle. It is also made up of rocks but they are in a molten condition so they are mobile enough to give mobility to tectonic plates. Their movement releases pressure and this pressure then travel unto the surface like waves. The place where pressure had released, which means an earthquake has come is called a source. Just above the source, the surface of the earth is called the epicenter. In 2011 a Rechtar 9.1 underwater earthquake came near japan followed by mega Tsunami waves. It was one of the deadliest natural disasters. It was so powerful that the earth’s axis has moved 8 c.m. Here one plate sunk underneath another one, a convergent boundary.
In short tectonic plates interact in three ways as convergent boundaries, divergent boundaries, and transform boundaries.
How tectonic plates behave?
On convergent boundaries, two plates move towards each other. In the case of the oceanic plate and continental plate the former sinks underneath the latter. That is how trench systems around the continents have originated. When two continental plates collide both of them uplift above. The Himalayan mountain range has formed like this at the junction of the Eurasian and Indian plate.
The divergent boundaries have characterized by the formation of ridges. Here two plates move away from each other leaving a weak spot for magma to rise which then solidifies as a portion of the plates themselves. All of the ocean have some portion of mid- Oceanic Ridge which encircles the whole globe. Here planet forms the very tectonic plates. The third type of boundary is Transform where two plates rub/move along each other in the opposite or same direction.
The mechanism of earthquake
On any of these boundaries, two plates interact and their joints are not airy with lots of space in reality the place is Jam-packed with no room. For them what is a little handshake can be Richter 9 earthquake for us. San Andrea’s fault in California USA is a famous transform boundary. Almost 99.9% of earthquakes happen at plate boundaries. The reason for this is that the joint between the two plates is not smooth. Some time plates can be altogether of different types like oceanic and continental plates or even if they are of the same type we are talking about miles thick solid rock layers. The solid chunks while interact produce lots of grinding and pressure.
The earthquake mechanism in subduction zones is simple. When two different kinds of plates one continental and other oceanic interacts they push against one another. This is a massive tension zone where two plates fight for the same spot. Now you might think why plates want to replace each other, they can simply be still. Fortunately, it doesn’t happen. I have mentioned about divergent boundary where two plates move away and new crust forms. Well, this happens just opposite the subduction boundary. The new crust gets created at the divergent boundary so the old one has to sink back into the earth.
When two plates fight for dominance heavier oceanic plate sink abruptly below and released pressure brings havoc in the name of an earthquake.
Tsunami is a Japanese term for huge columns of water that forms due to a disturbance in the seafloor. There are many reasons by which Tsunami can be created like volcanic eruptions, an underwater landslide, or the most important earthquake. It is quite clear that this mega-disaster can only happen in coastal areas. The biggest hotspot for Tsunamis is the ring of fire which not so ironically is also an earthquake hotspot. 70% of Tsunamis are end result of a mega-earthquake for example 2011 tragedy in japan. In simple words, subduction zones are an undisputed hotspot for earthquakes and Tsunamis.
The mechanism of Tsunami
I have explained above that how earthquakes are released during plate movement. A tsunami comes when the epicenter of an earthquake is an ocean. The earthquake waves replace columns of water and displace them in all directions. This wave travels just like a light wave but its intensity increase when it reaches shore. When Tsunami waves hit land their smooth flow gets blocked by it. The subsequent waves behind it feel increased blocked.
Think of a metaphor where you are standing in a line and it is moving at a certain speed. If something abruptly stops it the first person will abruptly stop and people being him will be stooped too. They will almost climb on him and push him forward. if more people are behind more push forward. Now think it in terms of Tsunami waves. Imagine abruptly stooped wave and many behind it when they will finally push forward and hit the land what disaster it would be.
In the coastal region, Tsunami is a mega problem. As the climate is warming and ice sheets are melting more water will enter oceans. Continents will lose their coastline and in this condition, Tsunami will be more devastating.
Read the following post on What causes a Tsunami?
How plate tectonics affect ocean circulation?
I have written a detailed post on ocean currents where I have mentioned how much the earth’s climate is shaped by ocean circulations. Now, these oceans have come to be in their current position due to plate tectonic. The motion of lithospheric crusts is responsible for every outcome on earth. To make you understand this concept let’s discuss Pangea, the most famous supercontinent.
The tough life on Pangea and the outcome of its assemblage
Pangea was made up of all the landmasses on earth, mostly situated in the southern hemisphere. There was no Atlantic ocean as The Americas were connected with Africa and Eurasia. A giant single ocean Panthalassa had surrounded Pangea from all sides. This single continent was not a very desirable place to live.
The moisture from the ocean couldn’t travel inland so there was an inhospitable desert in the middle of Pangea. Forests were only limited to coastal regions. On most of the Pangea, resources were very limited so it was a tough period to be around as a species. Now the position of Pangea was like a block that was stopping clouds to travel inwards. The coastlines were less and it shows us that maybe being one together is not a good idea. Pangea assembled as one landmass around 335 million years ago in the middle of the Carboniferous period. The Carboniferous period is indicated with large widespread coniferous forests. When Pangea assembled all those forests collapsed due to the unavailability of moisture. It’s a very famous event where these dead forests had made coal resources that we use now.
How ocean currents are being shaped now?
After the breaking of Pangea different oceans had separated continents and coastlines of continents increased. Ocean moisture got ways to travel inland. Ocean currents transport warmth to colder regions and keep their temperatures stable. For instance, The warm North Atlantic current carries heat towards northern Europe keeps things from freezing. Now, this current exists due to the current position of North America and Europe. Africa is splitting into two creating a big island with Ethiopia, Kenya, Tanzania, and Somalia. The Americas are moving away from Europe and in millions of years, the Atlantic ocean will be the biggest. These events will change the ocean circulation and eventually life on land. Forests will be deserts, mountains will be grasslands and valleys will be seas.
To have a general idea about different currents and how they flow refer to my blog post Ocean currents- The movement of life.
Are there Tectonic movements on other worlds?
No planet in the solar system or found outside to date had shown signs of the same plate tectonics as earth. All the other rocky planets have one giant shell around their mantle and gas giants are made up of gas so no possibility of crust. When the solar system formed around 4.6 billion years ago all the inner planets were molten and hot. Mercury and Mars are quite small and maybe have almost no amount of radioactive elements. They have lost their heat fairly early. Their cores are tiny, and most of the planets are solid balls now. Venus similar to earth doesn’t have a very profound core either and very few radioactive elements. Up until now, we have not found plate tectonics there.
The mega moons and Europa
The moons of gas giants can be a good bet for extra-terrestrial life as well as some kind of tectonic movements. For both of these parameters, our attention is on Europa, a moon of Jupiter. Europa is an Icy body with liquid subsurface oceans. Although, sunlight doesn’t reach Europa but Jupiter’s magnificent gravity had kept Europa from freezing to the core. Recently scientists have found ice slabs on Europa moving. The subsurface ocean works the same as the upper layer of the mantle which gives liquidity for ice slabs. Recent discoveries have found some kind of subduction zones in Europa. It was shallow subduction where one ice slab has been sinking underneath another. They have also found some kind of warm vapor chimneys near subduction zones which is similar to volcanic eruption on earth.
The Jovian moon IO and Saturn’s moon Enceladus are the most volcanically active bodies in the solar system. We can consider these two as potential spots for finding life too.
Journey out of the solar system
In recent years we have found countless exoplanets and among them, many are in the goldilocks zone. Scientists are using different ways to find out if those plants have plate tectonics or not. It is easier to find the major component of atmospheres but finding what rocks are made of is a tricky business. Nonetheless, in few years we will discover that how many exoplanets are actually habitable for life to even began and how many of them are habitable for complex life.
Read this post by Space.com on Europa, the potential candidate with plate tectonics.
Do we need plate tectonics for life?
This is a very tricky question. In my previous post plate tectonics 2.0, I have discussed how much life on earth is influenced by plate tectonics. Even before an active tectonic system, microscopic life was there but it sure had bloomed into complexity under the direct or indirect influences of plate tectonics. However, do we need plate tectonics for the origin of life? Maybe not.
Giant landmasses, the differentiation of layers, Lava, and Earth
We do have good chances of finding life on stagnant lid planet as long as they preserve their internal heat. First, we have to understand how planetary dynamics work. Let’s take the earth for example. Earth formed 4.5 billion years ago and it was all molten rock. Lava was flowing over it and meteor bombardment was a normal occurrence. The material on earth started getting differentiated as heavier matter sank down to the core and lighter had risen up to the surface. This matter differentiation had formed three distinct layers core, mantle, and surface. Almost all the planets and moons in the solar system have some kind of layer differentiation.
The outermost surface had kept on releasing heat out in the cold space as it cooled down. Gases and vapor kept on rising as the earth cooled. These gases formed the first atmosphere and cloud. Rains from those clouds as well as early meteor had filled the ocean with water. Earth got some kind of atmosphere and water-filled oceans. Now, this process still goes on. Volcanic eruptions release the heat and gases into the atmosphere that maintain the atmosphere. These gases mix with rainwater and fall on the surface. They got absorbed by the surface which is part of the curst (plates). These surfaces got recycled inside the earth after getting subducted through subduction zones. This is how everything works in unison.
The existing atmosphere of the earth remains due to the magnetic field produced by the iron core. This all had created conditions suitable for life to arise and got diverse. Plate tectonics recycles the whole surface and material-rich magma comes from within the depths of the mantle. In this way, material travels far and wide and no part left untouched.
Geology of the inner Rocky world
All the other rocky inner planets don’t have magnetic fields so there is nothing to protect their atmosphere from the sun. In spite of not having plate tectonics, stagnant lid planets do have volcanic activity. Volcanoes are the driving forces behind the maintenance of the atmosphere and climates which are essential for life. On the stagnant lid, we have shallower and weaker volcanoes. They erupt once in a long while and lava is also poor in minerals. However, these volcanoes were more active in past.
The origin of life on a stagnant lid planet is indeed a tricky question. Mercury and Venus have a tiny core so no magnetic field means no atmosphere. We all know how much important an atmosphere is for life. They are very close to the sun so temperatures are soaring high. Venus also has a carbon dioxide-rich atmosphere so you can think about the greenhouse effect. Moon and mars are far away from the sun but they again have the same core problem. In all of these planets, volcanic eruptions were very high at the time of their formation which is almost nil now.
Are Mega moons of gas giants a candidate for tectonism?
Gas giants don’t have a solid surface so no need of talking about plate tectonics. Moons of these gas giants are so far away from the sun that solar energy is unreachable for them. However, we know from evidence found on earth that life can survive without the sun. Many microorganisms on earth are chemo synthesizer, means they don’t depend on the sun for survival. We do have a candidate for life Europa, a Jovian moon. It might some kind of shallow plate tectonics which is not proved yet. It is an icy planet and Jupiter’s gravity is the main source of heat on Europa. Neptune and Uranus are so far away they don’t even get enough light not to mention solar energy. Their moons are also out of the question when life is concerned.
There is one important point though, plate tectonics are necessary for lasting habitable conditions. They increase volcanism that in turn releases carbon dioxide into the atmosphere which maintains the atmosphere. All rocky planets and moons were very volcanically active in past but now are very quiet. Without tectonic movement, new volcanoes don’t form and older ones can’t be tapped by the magma of the mantle. There are some exceptions though like Jupiter’s IO and Saturn’s Enceladus that are non-tectonic planets but very volcanically active.
Life outside of the solar system
This was all about the solar system but when we talk about exoplanets there are many Earth-like planets that have been identified. Out of these a lot of planets are in the goldilocks limit. To find life among other planets we have to abandon our normal understanding of life that we see around us. Life can survive without a star as we have a chemo synthesizer. Maybe life can develop without water. We have a general view that life needs water to survive and thrive. It is the best soluble as everything can mix in it. To find life in other places we have to change our perception about it and look from different perspectives.
- A brilliant post on plate tectonics and volcanism by National Geographic.
- Refer to this post on is earth the only planet with plate tectonics by Howstuffworks?
- An easily understandable post on tectonic plates on other planets by The geological society.
- Tsunami generation- earthquake by NOAA. A simple and informative read.
The forces which displace continents are the same as those which produce great fold-mountain ranges. Continental drift, faults and compressions, earthquakes, volcanicity, transgression cycles, and polar wandering are undoubtedly connected causally on a grand scale. Their common intensification in certain periods of the earth’s history shows this to be true. However, what is the cause and what effect, only the future will unveil.
Alfred l. Wegener
It is quite astonishing to think that almost all things on earth are shaped or affected by tectonic movements. Maybe this is the reason our planet is so different in the universe. What we have found nowhere and we should protect. The next post will be another awesome chapter on the History of earth. Another milestone that paved the way for our present. Until then stay tuned and do Revelation.
Originally published at https://www.thescientificrevelation.com on February 15, 2021.