Island History Pt. 2 Apocalypse

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Mountain Dust

When you think of Prince Edward Island, you likely picture its famous, vibrant red sand beaches, rolling green hills, and quiet coastal farmscapes. It is known as Canada’s “Gentle Island,” a peaceful province defined by its easygoing geography. But the true story of how PEI was formed is anything but gentle.

To understand the birth of Prince Edward Island, we have to rewind the clock back roughly 300 million years. We must travel to a time before the Atlantic Ocean existed, when the land that would become PEI was locked near the equator, trapped in the middle of a colossal supercontinent, and sitting in the shadow of mountains that rivaled the Himalayas.

Here is the dramatic, fiery, and watery story of how a tropical basin of mountain rubble eventually became Canada’s smallest province.

The Assembly of a Supercontinent

Our story begins in the Late Paleozoic era, during a time geologists call the Carboniferous and Permian periods. The Earth looked completely alien compared to the maps we use today.

The Earth’s outer shell, the crust, is not a single solid piece of rock. It is broken into massive jigsaw puzzle pieces called tectonic plates. These plates float on a layer of semi-liquid, superheated rock in the Earth’s mantle, constantly shifting and moving at about the speed your fingernails grow. Over hundreds of millions of years, these plates drift apart and crash back together.

Around 300 million years ago, a massive geological pile-up occurred. The Earth’s major landmasses—including what we now call North America, Europe, Africa, and South America—were slowly driven together by tectonic forces. They collided and fused into one gigantic, continuous landmass known as Pangea.

Because all the land was grouped together, Pangea had extreme climates. The coastlines were battered by massive ocean currents from the single global ocean, Panthalassa, while the deep interior of the supercontinent was essentially a massive, arid desert. The land that would eventually become Prince Edward Island was buried deep in this interior, located very close to the Earth’s equator. It was a hot, tropical environment, completely landlocked and far away from any ocean coast.

 The Mighty Appalachians

When continents collide, the rock has nowhere to go but up. Think of two cars in a slow-motion, head-on collision; the hoods crumple and fold upward into jagged peaks. When the tectonic plates carrying North America and Africa smashed into each other to form Pangea, the immense pressure buckled the Earth’s crust.

This collision created a massive, towering chain of mountains known as the Central Pangean Mountains. Today, the heavily eroded remnants of this ancient mountain range are split across the world—we know them as the Scottish Highlands in the UK, the Anti-Atlas mountains in Morocco, and, most importantly for North America, the Appalachian Mountains.

It is hard to imagine today, looking at the rolling, tree-covered peaks of the modern Appalachians, but 300 million years ago, these mountains were jagged, imposing, and incredibly tall. Geologists estimate that they were at least as high as the modern Rocky Mountains, and possibly as towering as the Himalayas.

The birth of Prince Edward Island is directly tied to the death of these mountains. As soon as the Appalachians were pushed up into the sky, the forces of nature—wind, rain, ice, and gravity—went to work tearing them down.

The Maritimes Basin 

As the towering Appalachian Mountains were relentlessly battered by ancient storms, the rock began to weather and erode. Massive rivers cascaded down the mountain slopes, acting like liquid conveyor belts. They carried millions of tons of boulders, rocks, pebbles, sand, and silt down from the high peaks.

Where did all this mountain debris go? It washed down into a vast, low-lying area called the Maritimes Basin. A basin is essentially a giant geological bowl or depression in the Earth’s crust. The Maritimes Basin was a massive valley that covered parts of what is now New Brunswick, Nova Scotia, the Gulf of St. Lawrence, and Prince Edward Island. At the time, this basin was located near the equator, creating a hot, seasonal, tropical climate characterized by intense monsoon rains followed by fierce dry spells. It was incredibly large: 150 square kilometers in area and up to 12 kilometers deep.

For millions of years, the rivers dumped sediment into the Maritimes Basin. As the water slowed down in the flat valley, it dropped its heavy load. Layer upon layer of sand, mud, and gravel piled up. Over unimaginable spans of time, the sheer weight of these layers pressed down on the sediment at the bottom. This immense pressure squeezed the water out and cemented the grains of sand together in a process called lithification, turning loose sediment into solid sedimentary rock.

Why is the Dirt Red?

The sediment washing off the ancient Appalachian mountains was incredibly rich in iron. Because the Maritimes Basin experienced severe dry seasons in its tropical climate, the rivers would often dry up, exposing the iron-rich sand and mud to the oxygen in the air.

When iron is exposed to oxygen and water, a chemical reaction occurs: oxidation. In simple terms, the iron rusted. The soil and the sandstone of Prince Edward Island are literally held together by ancient iron oxide, giving the entire province its iconic, fiery red coloration. PEI is, quite literally, made from the rusted, recycled rubble of an ancient mountain range.

The Breakup of the Supercontinent

Nothing in geology stays still forever. By about 200 million years ago, during the Mesozoic Era (the time of the dinosaurs), the heat building up beneath Pangea caused the supercontinent to bulge, crack, and eventually tear apart.

Rift valleys formed as the tectonic plates reversed course and began to pull away from one another. Magma from deep within the Earth surged up to fill the gaps, cooling to create brand new ocean floor. Slowly but surely, the waters of the global ocean flooded into these massive rifts. This was the birth of the Atlantic Ocean.

As the Atlantic Ocean grew wider, it pushed Europe and Africa to the east, and North America to the west. The massive block of continental crust carrying the Maritimes Basin—and the thick layers of red sandstone that would become PEI—began a long, slow journey northward.

Over millions of years, the tectonic plate carrying North America drifted away from the scorching heat of the equator and moved into the more temperate, northern latitudes where Canada sits today.

During this time, the thick layers of red sandstone in the basin were subjected to their own erosion. Because sandstone is a relatively soft sedimentary rock, rivers and winds easily carved valleys and hills into the landscape. However, at this point in history, Prince Edward Island was still not an island; it was simply a rolling, red-hilled region firmly attached to the rest of the North American continent.

In a game of Geographic What If, it is possible to explore the three other possibilities of the Pangea break up and the results for the Maritimes. If the rift had formed along the St. Lawrence River Valley, a weak and logical place for the rift to occur, the Maritime Basin would have remained a part of Africa. Charlottetown would now be on the west coast of Africa. 

If the the rift had occurred further east, the Maritime Basin would remain a part of Europe. The end result is bit more complicated to predict. The Maritime Basin would have become either an island chain or peninsula off of  Ireland or Spain.

The third and the mostly likely of all the outcomes is rather dire. And if the rift had been on both sides of the Maritime Basin, the Basin would have drifted into the Atlantic. As the plates moved, the surface crust would have lengthened and thinned. Eventually the land settled beneath the ocean to form a shallow sunken land mass.