Glass House Mountains: Modified Version of Continental Drift Or Plate Tectonics

Introduction

The glass house mountains are a group of large hills scattered across the sunshine coast region in Queensland Australia. The mountains received their names form the indigenous community however their shared name (the glass house mountains) was named by Lieutenant captain cook in 1770. Many ideas have been theorized regarding the formation of the mountains including several indigenous dream time stories, however, as scientific research has developed it is believed that the formation can be proven by the plate tectonic theory. In order to confirm this statement, it is necessary to discuss how the mountains have developed over the last 32 million years, the scientific theories that have led to the development of this claim, and a hypothesis concerning future volcanic activity in Australia.

Formation and Development

Scientists are confident that the formation of the Glass house mountains was not due to the subduction of tectonic plates because the continent of Australia is not near a plate boundary and therefore would not have been heavily affected if subduction had occurred. It was established that the formation of the mountains began 32 million years ago as the Indo-Australian plate moved over a large hotspot under the earth’s crust located in the asthenosphere. The hotspot applied immense pressure on the rock above, forcing magma through the weak sections in the crust. As a result, forming many active volcanoes scattered across the sunshine coast of Australia, now known as the glass house mountains. The hot spot and the volcanic activity covered large sums of the nearby land in a thick coating of basalt, leaving the molten plugs of the volcanoes covered and protected. As the tectonic plate continued to move in a north-easterly direction carrying the volcanoes away from the hotspot it allowed them to cool and become extinct as the magma supply had ceased. The plugs hardened to make extremely hard rhyolite and trachyte plugs under a layer of basalt. Over millions of years, the basalt covering the hardened plugs was weathered and eroded away exposing the plugs, this is how the extrusive mountains are known to this day.

Scientific Developments

Alfred Wegener, a meteorologist, developed the continental drift theory in the years 1908-1912. Wegener presented the idea that hundreds of millions of years ago all the continents were joined together as a supercontinent he had named ‘Pangea’, but over time have broken away. He believed this to be accurate because the borders of the continents seemed to fit together like a puzzle and groups of fossils were found to be connected over continents. In 1915 Wegener published a book explaining his discoveries and however fascinating it was not enough to convince the world of his theory. Many people did doubt his theory because not only was Wegener not a geologist, but he had made calculation errors in his published research. However, the largest flaw in his claim was that he was largely deficient in evidence regarding how the continents did separate due to the lack of technology at that time. The continental drift theory was mostly correct and although Wenger is not alive to witness it, the theory is now partially accepted by the scientific community.

Plate tectonics theory is the modified and scientifically approved version of the continental drift theory. Plate tectonics is the concept that the earth’s crust is broken into different plates that sit above the mantle. The movement of magma in the mantle (convection currents) cause the plates to contact, thus causing subduction zones, mid-ocean ridges, earthquakes, and tsunamis. There are three different types of plate boundaries, convergent (when the plates push together), divergent (when the plates pull away from the other), and transformed (when two plates slide past each other). This theory was developed using the help of modern-day technology that was not available to Wegener. GPS technology was used to confirm that the continents were indeed moving, magnetic readings detected the seafloor spreading, seismic monitoring found strong evidence regarding the earthquakes occurring along plate boundaries, and deep-sea drills and eco sounders assisted in the discovery of the ocean ridges. However, the fossil samples that Wegener had used were also a large part of developing the correct theory regarding plate tectonics.

Location of the Hotspot

Convection currents are the movements in the semi-plastic mantle that cause the tectonic plates to move. This occurs due to heat being unevenly distributed in the core of the Earth, thus heating different parts of the magma in the mantle causing parts to be less dense and rise, eventually cool and gain density and sink back below to the heated section and restart this process. This action triggers a circular motion in the mantle that pushes the plate above forwards into another. A convection current has been moving the Indo- Australian plate in a North-Easterly direction for longer than 32 million years. Geologists have theorized using satellite GPS technology that the Indo- Australian plate is moving approximately 7cm per year. Using the knowledge that the glass house mountains ceased all volcanic activity 26 million years ago (when the plate moved them from the hot spot) it is hypothesized that the hot spot is now located 1820 km from the last glass house mountain. Therefore, it is likely that the east Australian hot spot is now located just above the Tasmania region of Australia in the bastrait.

Hypothesis for the future

“The East Australia hotspot is a volcanic hotspot that forces magma up at weak sports in the Indo-Australian Plate to form volcanoes. The hotspot is currently located in Eastern Australia. Therefore, the Australian continent will have future volcanic activity.” This claim is a valid prediction of Australia’s future. Volcanic activity is likely to occur on the island of Tasmania because previous volcanoes formed in a roughly southwesterly direction due to the plate moving in a north-easterly direction. Tasmania is lined up in the same direction as the previous volcanoes formed on the main island and is directly south from Mt Schank and Mt Gambier which are the youngest Australian volcanoes/mountains, both erupted only 5000 years ago. Although it is not certain that the continent will experience volcanic activity, it is possible all activity will form on the oceanic crust to the side of Tasmania. However, lava fields have been already detected in Tasmania as a result of close proximity to the hotspot. If the activity does occur on the island of Tasmania it is unlikely to occur within the next million years and will not be nearly as substantial as the formation of the glass house mountains. Small fissure volcanoes or magma chambers are the extent of the expected activity to develop, this is due to the cooling of the hotspot over the period of time after forming the glass house Mountains. This can be inferred because the volcanoes that have developed in a southwest direction from the glass house mountains have decreased in size and have become less explosive.

Another hypothesis raised is the possibility of the convection currents converging the Indo -Australian plate and the Pacific plate to eventually cause a subduction zone and if large enough could eventually form volcanoes on the continent of Australia. However, this is unlikely for many millions of years and due to the continent’s placement on the plate.

Conclusion

In summary, the glasshouse mountains are a range of peaks located on the sunshine coast of Australia, formed by the Indo-Australian plate moving over a hotspot forming various volcanoes. The plate has been moving in a north-easterly direction for over 32 million years. As the volcanoes moved from the hotspot, they were cut off from a magma supply and began to cool. Over millions of years, the basalt exterior was eroded form the now extinct volcanoes, and the rhyolite and trachyte plugs were exposed. This information was uncovered using the modified version of continental drift (Alfred Wegener’s theory), called plate tectonics. It is hypothesized that the east Australian hotspot is currently located north of Tasmania in the Bastrait and will continue to produce volcanic activity in the future. The activity is expected to be located in Tasmania and be minor in comparison to the glass house mountains because the hotspot’s temperature has decreased throughout the last 32 million years.

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