ZEALANDIA: The undiscovered eighth continent of the Earth
by Rahul (narayan) Thapa
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| Zealandia Credit: GSA Today |
Today, I thought of a fascinating topic- the Zealandia- also
known as Te Riu-a-Maui (Māori) or Tasmantis. It is Earth’s undiscovered eighth
continent, which is facing a tough battle to become the eighth continent of that
world.
Without further ado, let’s get started!
Readers,
The hidden continent -Zealandia- made headlines in 2017 after a research paper with the working title Zealandia: Earth's Hidden Continent was published by GSA Today in its Volume 27 issue 3 (2017). However, even after four years of its scientific discovery, it has yet to receive worldwide recognition as a new continent. On the other side, by most standards, there is a total of seven continents at present- Australia/Oceania, Asia, Africa, and North America and South America, Europe, Antarctica, Figure 1 illustrates the world Map and continents, and Table 1 represents the total areas of each continent in sq. miles.
What was the GSA Today overview on Zealandia?
Recently in the year 2020, the Geological Society of America (GSA) stated that "Recent seafloor drilling has shown that dramatic elevation changes occurred between approximately 50 - 35 million years ago on the "hidden continent" of Zealandia, is a region of continental crust twice the size of - India - submerged beneath the SW Pacific Ocean. The infamous - Ring of Fire - in the western Pacific may have formed as a result of widespread reactivation of ancient faults, according to new research from this expedition that was just published in Geology."
In general, it is a landmass that is nearly entirely covered by the South Pacific Ocean. Only 4% of Zealandia rises above mean sea level, including New Zealand, and the remaining 96% of the landmass, or 5 million square kilometers, is underwater in the South Pacific, and "New Zealand" is the only largest part of the continent - Zealandia that is above sea level, followed on the North by New Caledonia.
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| Figure 1: World map with continents |
Table1: Name and Area of all the continents of the world.
Sr.No. | Name of the Continents | Total Area (in Sq.kms) |
1 | Asia | 44,127,508 |
2 | Africa | 298,34,614 |
3 | N. America | 24,243,886 |
4 | S. America | 17,741,013 |
5 | Antarctica | 12,610,490 |
6 | Europe | 9,996,090 |
7 | Australia | 7,617,930 |
#8 | Zealandia | 4,920,000 |
Figures 2 (a), illustrate the "Spatial limit of Zealandia" and Figure 2 (b) represents the area covered by the Continent of Zealandia. Therefore. through these Maps, it is confirmed that Zealandia is entirely situated in the southern hemisphere and surrounds New Zealand.
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Q1: Who is the creator of the concept of Zealandia?
Zealandia was given its name and general outline by Bruce Luyendyk in 1995. Other names for it include Tasmantis and Kiwi Land. The word Zealandia first appears in the book published in 1857 by Charles Hursthouse with the title New Zealand, or Zealandia: The Britan of the South Seas.
Wanna buy this book? just click on the - Amazon - It is already hyperlinked thanks to my efforts :D
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| Figure 2 (a): Spatial limits of Zealandia/ credit: GSA today |
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| Figure 2(b): Area covered by the continent of Zealandia Source: GNS Science |
Geology - Zealandia
In terms of geological time, the Zealandia continental crust submerged after severing ties with Australia 60–85 million years ago. At the time of its separation from Antarctica and Australia 80–130 million years ago, Zealandia made up 5% of the total area of Gondwanaland. Zealandia is currently acknowledged as the youngest, thinnest, and most submerged of all the continents. However, a study published in 2021 suggests that Zealandia may be up to 1 billion years old—roughly twice as old as geologists had previously believed.
The continent of Zealandia is made up of a wide variety of rocks, including limestone, granite, quartzite, schist, and siliceous continental rock. Its total area is roughly (4,920,000 square kilometers), which is the same size as our country, India (3,287,263 sq. km) However, unlike other continents, Zealandia is 94% submerged under the South Pacific Ocean and has much deeper and wider continental shelves. It is primarily made up of two nearly parallel ridges that are separated by a rift, which is where the continent's rift breakup stops and turns into a filled Graben Fault.
Friends, Understanding the million and billion years is tedious right?
Of course, it will be tedious because we can hardly fathom the geological timescale of the Earth. due to the fact that a human's lifespan is so brief compared to the duration of the Earth. The Earth works for millions and hundreds of thousands of years, whereas we humans only work for minutes, hours, days, and years. Therefore, for clear communication, Time is divided into eons, eras, periods, epochs, and ages by geologists (from longest to shortest). So, when it comes to the geologic timescale, timing is everything.
But remembering all of the aeons, eras, periods, epochs, and ages is incredibly difficult for all.
However, there is a simple way to understand the geologic time scale also referred to as the 'Calendar" for events in Earth's History. In this regard, the Geological "Clock" is one of the best ways to visualize the Geoglocial timescale.
Note:
- ‘Ka’ = ‘Kya’ (thousand),= 1,000 years ago
- ‘Ma’ = ‘Mya’ (million) =,1,000,000 years ago
- ‘Ga’ = ‘Gya’ (billion) =,1,000,000,000 years ago
Ok, let's do some Math!
"Each year has 365 days, right? so each day in the Geological clock represents 12.6 Mya ( 4.6 billion years /365 days). Each day has 24 hours, therefore, one hour represents 525,114 of the "Geological Year" [(4.6 billion years / (365 * 24)]."
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| Figure 3 Pie chart representing the Geological Clock |
This analogy might help you put the age of the Earth into perspective.
"If you consider the entire history of Earth to have occurred in a single day, the pie chart above represents a 24-hour clock. At twelve o'clock in the morning, the Earth is formed, and over the next few hours, it cools from a molten state. As the asteroid bombardment decreases, oceans begin to form. Before 4:00 am, extremely primitive single-celled life first appears, followed by photosynthetic organisms before 6:00 am. The atmosphere starts to become oxygen-rich just before noon. The single-celled eukaryotes have arrived by 1:00 pm (13:00 h). The first multicellular forms appear by 5:00 pm (17:00 h). It takes until after 8:00 p.m. before the first aquatic animals make an appearance. At 9:30 pm, plants begin to colonize the land; at 10:00 pm, animals do the same. For about an hour, from 10:40 to 11:40, the Dinos were the party's main attraction. At two minutes to midnight, the earliest hominids broke away from the rest, and at the stroke of midnight, modern humans appear."
Interesting Facts about Zealandia!
Q1: What is the highest point in Zealandia?
Mount Cook-Aoraki at 3724m will remain the highest point of the Zealandia continent.
Q2: What is the Crustal thickness of Zealandia?
In contrast to the typical thickness of the oceanic crust, which is 7 km, Zealandia's continental crust ranges in thickness from 30 to 46 km.
Q3: Zealandia is separated from Australia by which trough?
Geographically, Zealandia is divided from Australia by the CATO TROUGH, which is 3600 metres deep and covered in oceanic crust.
Note:
"As far as the number of continents is concerned many geologists of the world counts Europe & Asia as one giant continent called EURASIA so sadly the new addition of Zealandia doesn't seem to change the official number of the geological continent of the Earth."
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Q5: What was JODIES RESOLUTION?
Figure 4 shows the sailing picture of Jodies Resolution, a research expedition to explore Zealandia conducted in Sep 2017 by scientists connected to the IODP (International Ocean Discovery Programme) aboard the research ship JOIDES RESOLUTION. Different samples of sediments and rocks that were lying beneath the seabed were found by this drillship J.R. It also covered topics like plate tectonics, geology, extreme climates, and life on the ocean floor. Jerry Dickens, a co-chief scientist from Rice University in Texas, said that this area was crucial for examining global climate change. They added that it was a "Distinct geological entity" that "met all the requirements applied to Eath's other continents, i.e. Elevation, Distinctive Geology, Well defined area, and Crustal thickness."
Furthermore, in support of the aforementioned assertion, geologists from New Zealand, and Australia came to "the conclusion that Zealandia meets all criteria for being classified as a continent rather than a microcontinent."
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| Figure 4: Sailing picture of JODIES RESOLUTION |
The NSF Director, Jamie Allan, stated that the expedition provided insights into Earth's geological history, including the process of mountain-building in New Zealand, shifting tectonic plate movement, changes in ocean circulation, and changes in global climate.
According to Professor Rupert Sutherland of Victoria University in New Zealand, the expedition found "Big Geographic Changes."
Q6: Is Zealandia truly a continent?
Yes!
According to the US NSF (national science foundation), Zealandia was confirmed as a continent in 2017.
With a total area of about 4,900,000 km2, Zealandia is in fact substantially larger than any features referred to as microcontinents and continental fragments (1,900,000 sq mi). If Zealandia were to be considered a microcontinent, it would be the largest one ever created. Its size is six times greater than Madagascar, the second largest microcontinent in the world, and more than half that of the Australian continent.
Q7: What are the Criteria for becoming the new continent?
1-It must have Elevation above the surrounding area,
2- also distinctive geology with a well-defined area,
4-The Crust must be thicker approx (20km) than found in Oceanic plates.
5-In comparison to the ocean floor, the crust on land must be thicker.
6-In order to be considered a continent rather than a microcontinent or continental fragment, it must have "Well defined limits around a large enough area."
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Sources :
1:Sunken continent Zealandia used to be closer to the surface, with a very different climate | Stuff.co.nz
2:Scientists reveal secrets of lost continent Zealandia | Earth | EarthSky
3:What is Zealandia? Landmass under New Zealand that could become earth's eighth continent | The Sun
1:Sunken continent Zealandia used to be closer to the surface, with a very different climate | Stuff.co.nz
2:Scientists reveal secrets of lost continent Zealandia | Earth | EarthSky
3:What is Zealandia? Landmass under New Zealand that could become earth's eighth continent | The Sun