Introduction
Plate tectonics and biotic change are two fundamental processes that have shaped the Earth’s biodiversity over millions of years. Plate tectonics refers to the movement of the Earth’s lithosphere, which has resulted in the formation of different landmasses, oceans, mountains, and geological features. Biotic change, on the other hand, refers to the changes in the Earth’s living organisms over time, which have occurred due to various factors, including climate change, natural disasters, competition for resources, and evolutionary processes.
The movement of tectonic plates has created different biogeographic regions and isolated species, leading to the development of unique biodiversity in different parts of the world. For example, the separation of continents has allowed for the evolution of distinct flora and fauna in different regions. On the other hand, plate tectonics has also contributed to mass extinction events, such as the extinction of dinosaurs, by creating changes in climate and sea level.
Biotic change has also played a significant role in shaping the Earth’s biodiversity, with species adapting to changing environments, and new species evolving over time. The interplay between biotic and plate tectonic processes has led to the formation of complex ecosystems and the diversity of life on Earth.
In this context, understanding plate tectonics and biotic change is essential to better comprehend the evolution of life on Earth and how it may continue to evolve in the future.
Plate Tectonic and Biotic Change and Biodiversity
Plate tectonics and biotic change have played a significant role in shaping the Earth’s biodiversity over millions of years. Plate tectonics is the study of the movement of the Earth’s lithosphere, which consists of the crust and the uppermost part of the mantle. The lithosphere is broken into several large pieces called plates that move relative to each other over time. This movement has affected the distribution of landmasses and oceans on the Earth’s surface, as well as the climate and geological features such as mountains and volcanoes.
Biotic change, on the other hand, refers to changes in the Earth’s living organisms over time. These changes can occur due to various factors, such as climate change, natural disasters, competition for resources, and evolutionary processes.
The movement of tectonic plates has had a profound effect on the Earth’s biodiversity. As plates move apart, new ocean basins are formed, and as plates collide, mountains are created. These processes have led to the formation of different biogeographic regions and the isolation of different species, which has led to the development of unique biodiversity in different parts of the world.
For example, the separation of the South American and African plates millions of years ago created a barrier that prevented the exchange of species between these continents. This isolation led to the development of unique flora and fauna in each region, such as the evolution of marsupials in Australia and the development of a diverse array of primates in Africa and South America.
Plate tectonics has also played a role in major extinction events throughout the Earth’s history. For example, the breakup of the supercontinent Pangaea about 200 million years ago led to significant changes in the Earth’s climate and sea level, which resulted in the extinction of many species, including the dinosaurs.
Plate Tectonics
A theory that states that the earth’s crust is made up of a number of plates that move over a liquid crust that get created and destroyed over time.
Plate tectonics is a scientific theory that explains how major landforms are created as a result of Earth’s subterranean movements. The theory, which solidified in the 1960s, transformed the earth sciences by explaining many phenomena, including mountain-building events, volcanoes, and earthquakes.
In plate tectonics, Earth’s outermost layer, or lithosphere—made up of the crust and upper mantle—is broken into large rocky plates. These plates lie on top of a partially molten layer of rock called the asthenosphere. Due to the convection of the asthenosphere and lithosphere, the plates move relative to each other at different rates, from two to 15 centimeters (one to six inches) per year. This interaction of tectonic plates is responsible for many different geological formations such as the Himalayan mountain range in Asia, the East African Rift, and the San Andreas Fault in California, United States.
Plate tectonics is the scientific theory that describes the movement and interactions of the Earth’s lithosphere, which is made up of the crust and the uppermost part of the mantle. According to this theory, the lithosphere is divided into several large plates that move slowly over time due to the convective movements of the mantle beneath them.
The boundaries between these plates are characterized by intense geological activity, such as earthquakes, volcanic eruptions, and the formation of mountain ranges. There are three main types of plate boundaries:
- Divergent boundaries: where two plates move away from each other, leading to the formation of new oceanic crust and mid-oceanic ridges.
- Convergent boundaries: where two plates move towards each other, leading to the formation of mountains, volcanic activity, and the destruction of oceanic crust through subduction.
- Transform boundaries: where two plates slide past each other horizontally, leading to earthquakes and the formation of transform faults.
The study of plate tectonics has contributed to our understanding of the Earth’s geological history, the formation of mountain ranges, the location of mineral resources, and the distribution of landmasses and oceans. It has also helped explain the occurrence of natural disasters, such as earthquakes and volcanic eruptions, and their impact on human populations.
Moving Plates
The force for these movements is derived from magmatic convection cells in the asthenosphere of the mantle. The upward portion of these cells are known as magmatic plumes. When they hit the crust, the plate above is melted and forced to spread creating a spreading ridge as they are adding new continental material (constructive margin) to the edges of these plates.
The movement of plates is a fundamental aspect of plate tectonics, which explains the interactions and movements of the Earth’s lithosphere, or outermost solid layer, consisting of the crust and the uppermost part of the mantle. The movement of plates occurs due to the forces generated by the convection currents in the mantle below the lithosphere.
At divergent boundaries, where two plates move away from each other, the mantle below the lithosphere rises to fill the gap, creating new oceanic crust. This process is known as seafloor spreading, and it is responsible for the widening of the Atlantic Ocean.
At convergent boundaries, where two plates move towards each other, the denser oceanic plate is subducted, or pushed down, beneath the less dense continental plate, leading to the formation of mountain ranges and volcanic activity. This process is responsible for the formation of the Andes Mountains and the Ring of Fire around the Pacific Ocean.
At transform boundaries, where two plates slide past each other horizontally, the movement can cause earthquakes, such as the San Andreas Fault in California.
The rate of plate movement varies depending on the location and type of boundary. For example, the rate of movement at the Mid-Atlantic Ridge is about 2.5 cm per year, while the rate of movement at the Nazca Plate along the western coast of South America is about 6-7 cm per year.
Evidence Supporting Plate Tectonics
Ages of oceanic crusts get older as one moves away from a spreading ridge. The ages of oceanic sediments on top of the crust get older as one moves away from a spreading ridge.
Rock formations with the same mineral content and age existing on opposite continental shores. The eastern most tip of South America and the African Congo both have the same iron ore rock formation. Rock formations are also shared between Newfoundland, Canada, and the west coast of Ireland and southern India and South Africa.
Magnetic anomalies showing variations in the Earth’s magnetic field strength are arranged in bands parallel to each other on either side of the spreading ridges. Magnetic polarity reversal patterns are preserved as the rock forms, showing symmetry about spreading ridges. The margins or edges of some continents have shapes that indicate that they once fit together. (i.e. South America fitting into Africa.)
There are several lines of evidence supporting the theory of plate tectonics, including:
Paleomagnetism: The Earth’s magnetic field has reversed several times over millions of years, leaving a record of magnetic stripes on the ocean floor. The pattern of these magnetic stripes indicates that the oceanic crust has been spreading out from mid-ocean ridges, supporting the theory of seafloor spreading.
Earthquake and volcanic activity: The majority of earthquakes and volcanic activity occur at plate boundaries, supporting the theory of plate movement and the interactions between plates.
Distribution of rocks and fossils: The distribution of rocks and fossils on different continents provides evidence of the existence of land bridges that have since been separated by the movement of plates. For example, identical fossils have been found on opposite sides of the Atlantic Ocean, indicating that the continents were once joined together.
Continental drift: The fit of the Earth’s continents, particularly along the Atlantic Ocean, is another piece of evidence supporting the theory of plate tectonics. The continents appear to have once been joined together, forming a single supercontinent called Pangaea.
The combination of these lines of evidence provides strong support for the theory of plate tectonics and the movement of plates. The theory has revolutionized our understanding of the Earth’s geological processes and has allowed us to better predict and understand natural disasters, the formation of mountain ranges, the location of mineral resources, and the evolution of biodiversity.
Evolution and Biodiversity Influenced by Plate Activity
Pangea
Two hundred million years ago (Ma), research suggests that all the continents where one large mass which was named Pangea.
Terrestrial organisms were able to migrate across all continents and were only limited by their biotic potential.
Pangea was a supercontinent made up of all of Earth’s land masses.
Alfred Wegener came up with the theory in 1912.
Broken up by plate tectonics
The explanation for Pangaea’s formation ushered in the modern theory of plate tectonics, which posits that the Earth’s outer shell is broken up into several plates that slide over Earth’s rocky shell, the mantle.
Pangaea broke up in several phases between 195 million and 170 million years ago. The breakup began about 195 million years ago in the early Jurassic period, when the Central Atlantic Ocean opened, according to the chapter. The supercontinent fractured largely along previous sutures.
Gondwana (what is now Africa, South America, Antarctica, India and Australia) first split from Laurasia (Eurasia and North America). Then about 150 million years ago, Gondwana broke up. India peeled off from Antarctica, and Africa and South America rifted, according to a 1970 article in the Journal of Geophysical Research(opens in new tab). Around 60 million years ago, North America split off from Eurasia.
Biodiversity
As Pangea began to separate into separate continents 130 Ma, created physical barriers such as seas, restricting migration within the continents.
Gene pools of species are separated and as they are exposed to different physical (i.e. climate) and biotic (i.e. change in predators) conditions, each portion of the species adapts differently and eventually forms new species on the separated continents.
This process is known as speciation.
Changes in physical and biotic conditions will also lead to the creation of new species increasing the diversity of habitats and niches.
This also provides the space for new species to evolve into these habitats.
The end result of the separation of Pangea into today’s continental configuration is that plate tectonics has been one of the main driving forces promoting biodiversity or organisms.
In addition to continents separating, some like India left south Africa and Antarctica and joined up with Asia.
It took with it organisms that were typical to Antarctica and Australia.
Over the next 100 Myers, these organisms evolved in isolation from any other continent until they formed a land bridge with Asia.
Since 30 Myers ago the species in India and Asia have been re-adapting themselves causing additional biodiversity.
Australia has one of the most unique sets of organisms as it and Antarctica have been separate from all the other continents for the last 130 Myers.
Australia separated from Antarctica about 50 Years ago.
This extreme isolation over such a long period of time supports Darwin’s theory of evolution in that this part of the world has the most unique organisms.
Australian species have had such limited contact with species from other continents that they have only needed to adapt to their particular set of species and climate.
No re-adaptation to other species from other continents has occurred until the arrival of the Europeans.
The splitting up of Pangea 200 million years ago had the following effects on species
diversity and distribution.
- Species gene pools or populations where split as Pangea separated.
- New habitats were created due to a change in biotic and abiotic factors such as climate (temperature and moisture), changes in species relationships, and topography.
- New niches were made available and filled causing further adaptation of species to new conditions thus modifying the local ecosystem.
- Species relationships change with respect to mutualism, predation, and competition. Species need to modify food source, protection, and dependence patterns in the food web.
- Speciation: is the creation of a new species when a gene pool of one species is split, and exposed to new conditions to which each pool adjusts to. Different genetic traits are passed on to offspring. A new species evolves once the 2 original populations cannot mate.
Rejoining of plates such as India and Asia. 30 Ma ago caused the following.
- Migration of one species into the territory of another introduces new forms of competition and predation that existing species need to adapt.
- Further speciation is generated and modified as they come into contact with a variation of the original gene pool.
Extreme isolation such as Australia and Antarctica. 130 Ma of isolation.
- As no new predators are introduced over a long period of time speciation is limited to changes in abiotic factors such as climate and topography.
- Evolution tends to slow down and become more specialized if there are fewer stresses and ecosystem changes.
- Species evolve separately from the original gene pool and tend to be very different from other areas with more contact with the original gene pool.
Plate Tectonics and Biotic Change
The biogeographic regions of the world that Wallace recognized roughly coincide with the continents themselves. But in the twentieth century, scientists have recognized that biogeography has been far more dynamic over the course of life’s history.
In 1915 the German geologist Alfred Wegener (left) was struck by the fact that identical fossil plants and animals had been discovered on opposite sides of the Atlantic Since the ocean was too far for them to have traversed on their own, Wegener proposed that the continents had once been connected. Only in the 1960s, as scientists carefully mapped the ocean floor, were they able to demonstrate the mechanism that made continental drift possible — plate tectonics.
Biogeographers now recognize that as continents collide, their species can mingle, and when the continents separate, they take their new species with them.
Africa, South America, Australia, and New Zealand, for example, were all once joined into a supercontinent called Gondwanaland. The continents split off one by one, first Africa, then New Zealand, and then finally Australia and South America.
The evolutionary tree of some groups of species — such as tiny insects known as midges — shows
the same pattern. South American and Australian midges, for example, are more closely related to one another than they are to New Zealand species, and the midges of all three land masses are more closely related to one another than they are to African species. In other words, an insect that may live only a few weeks can tell biogeographers about the wanderings of continents tens of millions of years ago.
Alfred Wegener
Alfred Wegener (1880-1930) was a German scientist who proposed the theory of continental drift in the early 20th century. The theory of continental drift proposed that the continents were once joined together in a supercontinent called Pangaea and have since moved apart to their current positions. This theory was later incorporated into the theory of plate tectonics.
Wegener first presented his theory of continental drift in 1912 in his book “The Origin of Continents and Oceans.” He based his theory on several lines of evidence, including the fit of the coastlines of South America and Africa, the distribution of fossils across different continents, and the similarities in rock formations across continents.
Despite his evidence, Wegener’s theory of continental drift was not widely accepted during his lifetime. Many scientists at the time could not explain how the continents could move through the solid Earth, and the theory was met with skepticism.
It was not until the 1950s and 1960s, with the development of new technologies, such as sonar and satellite imagery, that the theory of plate tectonics was developed. This theory incorporated Wegener’s ideas of continental drift, as well as the concept of seafloor spreading and the movement of tectonic plates.
Today, Alfred Wegener is recognized as a pioneer in the field of plate tectonics and his theory of continental drift is considered a significant contribution to the understanding of the Earth’s geological history.
Wegener found that the distributions of fossils of several organisms supported his theory that the continents were once joined together.
100 years ago, German geophysicist Alfred Wegener presented his theory of continental drift – the idea that the continents of Earth are gradually drifting apart. And now we have some compelling new information.
Wegener’s theory was partly based on the observation that the large landmasses of Earth fit nicely together like a puzzle but it was also supported by evidence of the same fossilized plants on opposite sides of oceans.
Wegener argued that all the earth’s land masses were once assembled into one large coherent continent, a supercontinent later named Pangea.
Wegener’s theory has now been replaced by the theory of plate tectonics – an extension of continental drift theory that suggests continents migrate due to the movement of the tectonic plates on which they lie.
Today, the theory of plate tectonics is the foundation for understanding geodynamics – the movement of the earth’s surface – at the most basic level. Plate tectonics can help explain why Hawaii is “followed” by a chain of islands and how mountain chains form by the collision of continental plates.
The Earth’s crust has been found to be composed of several distinct plates.
To understand these processes we have to invoke a major change in geodynamics. We need a theory that can explain how the earth’s surface was changing prior to 3.2 billion years ago. And to get there we need to a lot more research.
A century ago, Wegener laid out the path to understanding the geodynamic processes behind the development of the earth. But we now have to acknowledge that when we look back in time, there have been considerable changes in the geodynamics of the earth.
Understanding these changes is essential if we want to learn more about the early development of Earth and the conditions affecting the climate and environments under which life on Earth began.
Conclusion
Plate tectonics plays a crucial role in shaping the Earth’s surface and has had significant impacts on the evolution and diversification of life on our planet. The movement of tectonic plates has led to the formation of mountain ranges, the opening and closing of oceanic gateways, and the creation of new habitats for organisms. These changes have driven the evolution of new species and contributed to the high biodiversity we see on Earth today.
However, plate tectonics is also associated with natural hazards such as earthquakes, volcanic eruptions, and tsunamis that can have devastating consequences for both humans and ecosystems. The movement of plates has also been linked to mass extinction events in the past, highlighting the need for continued research and understanding of this dynamic process.
References
- Dr. M.B.POTDAR (Professor Shivaji University Kolhapur)