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Volcanoes: The rise and fall of continents

Updated: Apr 21, 2023

The Earth has gone through 4.6 billion years of transformation. This blue planet, that we call home, has many layers. With the heavier elements sinking to the mostly iron core, and the lighter elements existing in our atmosphere.

Anatomy of Earth. Image credit: Yuri Arcurs/ Istock/ Getty Images Plus


The Earth features areas of different ages. For example, continental crust, which is the outermost layer of the Earth, tends to be older than the oceanic crust. This is due to the subduction process, where denser oceanic crust sinks under the lighter continental crust and into the mantle. Some continental crust could even date back to about 4.4 billion years old, such as that found in Australia.

The crust and the upper mantle make up a section of the Earth that scientists call the lithosphere. The lithosphere is divided into sections, dubbed tectonic plates.

Earths layers. Image Credit: USGS


According to the theory of plate tectonics, the tectonic plates move over the asthenosphere, which is the molten upper part of the mantle. This movement allows for oceanic and continental plates to either move towards or away from each other. Causing the land masses on Earth to look different throughout time.

According to the National Oceanic and Atmospheric Administration (NOAA) in the US, about 60% of the currently active volcanoes are situated between the boundaries of tectonic plates. The majority of volcanoes are found in an area that is called the "Ring of Fire," which goes around the Pacific Ocean. Additionally, some volcanoes are above areas called hotspots, which are in the mantle and are anonymously hot.

Volcanoes play an interesting role in the rock cycle. Where subduction is the sinking of dense rock to the mantle, volcanoes are the area where less dense molten rock (magma) rises to the surface of Earth (where it becomes lava) and eventually cools becoming extrusive igneous rock. There are plenty of different lava flows, as well as different rocks produced. To look at specific rocks, check out this explore tool by the UK Virtual Microscope.

It is near an active volcano where you will find the newest rock on Earth! This is also where some volcanic islands form such as Hawaii and Tonga.

Volcanic eruptions occur about 50-60 times per year. At a given moment, numerous volcanoes are erupting globally though often they are less publicised, not immediately threatening, and being closely monitored by local observatories.

A recent eruption, that has perplexed scientists is that which occurred at Hunga Tonga-Hunga Ha'apai in the Tongan archipelago, starting on 20th December 2021. This volcano is located just 65km North of Tongatapu, the main island of Tonga. It is a part of the Tonga-Kermadex Islands volcanic arc which is a subduction zone between New Zealand and Fiji. The island has 74,611 residents. This is a submarine volcano, meaning that it is submerged underwater. Nonetheless, its climax on the 15th of January resulted in a massive plume that extended about 58 kilometers into the mesosphere and could be seen by various satellites. The acoustic shockwave also caused a disruption in the ionosphere.

It can be incredibly difficult to accurately determine when a volcanic eruption will occur. A Tongan proverb says "Motu ka na’e navei," which means "to always be prepared for a disaster." The volcanic eruption left 3 people dead and impacted over 80% of the population. The subsequent tsunami also reached Japan, the US, New Zealand, and other countries within the Pacific Ocean region. This further highlights the need for disaster preparedness and response.

The United Nations Environmental Programme (UNEP) created an Awareness and Preparedness for Emergencies at Local Level (APELL) Handbook with the aim to aid local leaders in preparing for disasters and building resilience in order to mitigate property damage etc.

As the effects of climate change become more prevalent, being prepared for natural disasters becomes increasingly important. In this article, written by galaxy digital, disaster relief organizations are listed.

Furthermore, if you wish to donate to help support those impacted by the Tonga eruption please find relevant links below:

For more information on how to donate safely to help those in Tonga, visit the Council for International Developments page.


This article was co-written by Rachel Bisland, who completed her undergraduate and MSci at University College London (UCL) in Earth sciences, and is currently a Ph.D. researcher at the University of Leeds studying the use of satellites in contributing to more accurate volcanic forecasting.


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