How Island Chains Form

How Are Island Chains Created?

Island chains are a common destination for boating enthusiasts. They're beautiful, they’re surrounded by water, and there are usually many individual islands in a row, giving you plenty of land to explore. But how exactly are these island chains formed? And what are the best ways to appreciate them?

How Island Chains (Archipelagos) Are Formed

Island chains, sometimes called archipelagos, are groups of islands relatively close to each other and, typically, formed in a line – thus forming a kind of visual “chain.” In English, multiple island chains are named “Keys,” though this isn’t a strict requirement. Hawaii, for example, is an island chain.

How are these island chains formed?

Let’s start by talking about how islands are formed. We naturally think of islands as a permanent and timeless feature of the Earth, but new islands are forming all the time; they’re just forming so slowly that they’re hard to notice.

Realistically, islands can be created in many different ways. When moving continents collide with each other, the resulting impact can create island remnants. Deposits of sediment and glacial retreats can also cause new islands to form. But the most interesting and most common ways that islands appear is through tectonic activity.

Deep below the Earth’s crust is a layer of the planet called the mantle. The mantle is made of molten rock, which naturally flows with currents – much like the currents of the ocean. This underlying current results in movement of “tectonic plates” which float on top of the mantle. The movement of tectonic plates is responsible for earthquakes, continental movements, and most importantly, the formation of volcanoes.

When tectonic plates are pushed together and pulled apart, they lead to volcanic activity; when plates are pulled apart, it can cause an eruption of hot magma. Hot liquid magma eventually cools, forming a solid. And over time, entire islands can form from these solids.

Interestingly, volcanoes can sometimes form in the middle of a tectonic plate, causing magma to rise up until erupting on the bottom of the sea. Geologists call this a hot spot.

The Hawaiian Island chain was formed by such a hot spot in the Pacific Ocean. The hot spot is totally fixed, periodically erupting with magma. At the same time, the tectonic plate above it is almost constantly moving. Because of this, when the undersea volcano erupts and forms a new island, the island gradually shifts away (relative to the position of the hotspot). When the volcano erupts again, the first island is far away, allowing a new island to pop up just a few miles to a few hundred miles away.

This process can repeat indefinitely, leading to the ongoing creation of new islands in the chain. The Hawaiian archipelago has been undergoing this cycle of creation for millions of years – and now features 132 different islands, atolls, reefs, shallow banks, shoals, and seamounts, sprawling across more than 1,500 miles.

The Canary Islands are another example of an island chain that formed in a similar way to the Hawaiian Islands.

In short, island chains form when an underwater volcano erupts many times over millions of years; thanks to tectonic plate shifts, the position of the islands change relative to the volcano, making room for new nearby islands.

The islands of the Maldives were formed in the same way as the Hawaiian Islands, but they look so different. The Hawaiian Islands are mountainous whereas the Maldives are low-lying coral islands. In fact, the highest natural elevation of the 1,192 islands making up the Maldivian archipelago is just 2.4 metres above sea level, located on Vilingili Island in the Addu Atoll.

So why are coral island chains, like the Maldives so different to islands like Hawaii and The Canaries? The answer is age. The Maldives are much older – they began forming 68 million years ago, whereas the oldest Hawaiian island formed only 5 million years ago, and Fuerteventura, the oldest of the Canary Islands formed 22-23 million years ago.

But how did the ancient volcanoes of the Maldives turn into coral islands? When the volcanic activity stopped, the volcanoes gradually sank beneath the ocean – erosion and cessation of the upward pressure from the hot spot magma plume both playing a part.

A fringing reef of coral formed around the edge of each volcano where the sea was shallow enough for sunlight to penetrate. As the volcanoes continued to subside the coral kept growing. Once the centre of a volcano subsides, what is left is a ring of barrier reef coral around a central lagoon. So, each volcano in the chain produces one coral atoll – a circle of islands surrounding a lagoon. This is why you’ll often have a calm lagoon side and a rougher ocean side on a Maldivian island.

The action of the sea breaks up the coral to form coral sand, and the living coral is continually growing and being replenished.

Given the right conditions, the Hawaiian and Canary Islands may look more like the Maldives in tens of millions of years’ time.

New Islands to Explore

Are you sad that full island chains can sometimes take millions of years to form? Don’t fret! New islands are constantly emerging. In fact, there are at least 8 new islands that have formed in just the past 20 years. For example, there’s Hunga Tonga, which created a new island in the South Pacific between December 19, 2014 and January 16, 2015; you’ll have to act fast to see it, however, as scientists estimated that the island will completely erode in just a few decades.

And the Hawaiian Island chain keeps adding new components – the Lō'ihi Seamount is currently 3,200 feet below sea level and is expected to be the next addition to Hawaii. Don’t get too excited for this one, though. It’s only growing in height by a few centimetres per year, so it might be tens of thousands of years before it fully emerges.

Making the Most of Beautiful Island Chains

One of the best ways to enjoy your boat is to tour a full island chain.

How do you make the most of it?

  • Understand that every island chain is different. First, realize that every island chain is unique. Visiting Hawaii isn't the same as visiting the Greek islands, nor is it the same as visiting the Caribbean islands. Every island chain in the world has unique landscapes, cultures, and attractions to explore. Get out there and see them all!
  • Plan in advance. While there's nothing wrong with a bit of improvised exploring, you should also research and plan in advance if you want to make the most of your trip. Pay attention to the best attractions on each island and what makes each island in the chain unique.
  • Take your time. You're going to get more out of your vacation if you take your time. Don't rush from one island to the next just to make sure you see them all; the journey is part of the experience.
  • Leave room in your schedule. Always leave some extra room in your schedule so you can spend more time doing the things you enjoy most. If you fall in love with one island in the chain, consider spending an extra day or two there.
  • Ask the locals for tips. The locals know best. These are the people who are most familiar with these islands and what they can offer, so hit them up for some recommendations. Ask about the beautiful and interesting things that most visitors miss!

Are you thinking about a beautiful, relaxing vacation to an island chain near you? You’ll enjoy it more in a new boat. If you’re in the market for a bigger, better yacht, or if you’re just looking for a simple upgrade, check out our vast selection of new and used boats for sale today!

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