T-shirt slogans aside, the pursuit of Geology is to understand terra firma – the foundation on which life grows and the earthly roots upon which we exist.

We’ll follow the journey mapped out by geologists who travel the world seeking to answer questions about how Earth is made, stumbling upon beautiful landscapes, deep-rooted riches and soaring spectacles as they explore. We begin in America.

1. Say Hello to the Arizona Wave

Arizona: Home of the Grand Canyon, the Cardinals, and this marvel of nature popularised by computer screensavers the world over.

 Famous Geology rock formation in Pariah Canyon

You can see why. Never has a landscape undulated with such grace and vibrancy while oxymoronically seeming inhospitable and arid. The ripples in the sandstone seem so smooth, they might have been formed by a giant running their fingers through paint.

In fact, the Wave is Navajo Sandstone dating back to the Jurassic age which, over time, has been eroded by wind and water to create two U-shaped troughs. They are only reachable by hiking across rugged, trackless desert to the slopes of the Coyote Buttes in the Paria Canyon-Vermilion Cliffs Wilderness. The land is closely guarded and only the lucky few who win a lottery permit may pass into the territory to ride the Wave – but tread carefully because the ridges and ribbing of this soft sandstone are easily broken.

In some areas, geologists have noted deformities within the Wave. Judging from their physical characteristics, they likely represent the trampling and churning of these sands by dinosaurs.

So, geologically, the screensaver-worthy scene paints a colourful picture of the Earth’s past as bright as the oranges and reds of the sandstone itself. Not to mention, the Wave looks like a topographical map on Earth’s very landscape.

Perhaps, subconsciously, this is what draws geologists – the people who map out our world – to its peaks and troughs.

2. The Mystery of Death Valley’s Sliding Rocks

But we must move on. Heading North-West towards California, we make a stop at Death Valley for a little intrigue puzzled over by observers and chin-scratchers for centuries – until some scientists came along to solve the mystery.

Racetrack Playa. A 'Sailing Stone' photographed at night under the Milky Way at California's Death Valley National Park at the Racetrack Playa

On the dried up, almost perfectly flat lake bed of Racetrack Playa, silt and clay sediment sits largely undisturbed and watched over by steep surrounding mountains. However, sometimes tracks as long as 1,500 feet snake across the Racetrack Playa, leaving smooth lines cutting through mud cracks. They’re left by rocks, some of which weigh hundreds of pounds. It seems the heavy, inanimate rocks, which found their way to the lake bed from the mountains through erosional forces, have been dragged across the playa. But the undisturbed sediment surrounding the trails eliminates the possibility of human or animal involvement.

Which begs the question – how are the rocks moving? In this geological mystery, hurricane-force winds, dust devils, and slick algal films have all been theorised.

Some pointed to prevailing winds blowing southwest to northeast across Racetrack Playa. But the weight of the embedded rocks disproved the theory. Others thought the motion was aided by thick ice sheets strong enough to carry the rocks. Here, it rains just a couple of inches per year and the steep mountains act as a funnel, depositing runoff and turning the bed into a shallow lake. Extremely rarely, it will freeze over. But this theory suggested the ice must be thick enough to carry the rock’s weight.

In August 2014, scientists set up for what they expected to be the most uninteresting experiment ever – and solved the mystery. They found the phenomenon is actually caused by a unique combination of the previous theories.

First, rain runoff fills the playa with water deep enough to allow for the formation of floating ice during cold winter nights but shallow enough to expose the rocks. Temperatures plummet at night far enough for the pond to freeze and form sheets of ‘windowpane’ ice, thin and light enough to move freely but thick enough to maintain strength. Then, when the sun comes up, the ice begins to melt and break up into large, floating panels driven across the playa pool. The ice sheets can then, and only then, push these rocks in front of them so the moving stones leave trails in the soft mud bed below the pool surface.

Mystery solved. Onto our next geological dance.

3. The Electric Blue Glacier Caves of Iceland’s Jökulsárlón Glacier Lagoon

This dance is largely about dodging other tourists. Iceland’s landscapes are renowned for encompassing the best of what geology has to offer. With towering waterfalls, geysers and geothermal hot springs, the beauty and the lifestyle combine for a perfect trip.

However, we’re heading to a colder, darker and more perilous spot nestled underneath tonnes of ice.

Blue crystal ice cave and an underground river beneath a glacier in Vatnajokull National Park

Covering 8% of Iceland, the Vatnajökull glacier – literally translated as Glacier of Lakes – is Europe’s largest outside the Arctic. Glaciers are unique in the way they creep across miles of land and mountains, covering volcanoes with their compacted mass of snow and ice – an unstoppable force of their own mass.

However, glaciers are retreating and even disappearing at the hands of climate change. Iceland mourned the loss of the glacier called Okjokull in 2019, after the warmest July on record. Scientists have warned 400 other glaciers are also at risk. They fear all of the island’s glaciers will be gone by 2200.

For now, the Vatnajökull glacier remains home to beautiful, naturally occurring glacier caves. Like most others, the glacier caves are carved out by water running through or under the glacier’s ice as the glacier melts and moves downward on its gravitational path. These ice caves – named Crystal, Blue Diamond, and Northern Lights, among others – are beloved for their electric blue colour. The glacial ice is so thick, dense and old that it absorbs all colours of the spectrum except the colour blue. Here, a single glacier ice crystal can grow to be as large as a baseball.

Jokulsarlon Beach (Diamond Beach) with giant ice rocks on the lava black sand beach Ice rocks often end up on the black sands of Jökulsárlón beach – vast coastal stretches composed of ash from the frequent eruptions of nearby subglacial volcano, Grímsvötn. These so-called ice diamonds are brought to the coast by glacial floods and lend Jökulsárlón its nickname of Diamond Beach.

4. Diamonds: The Misunderstood Mineral

From the ice diamonds of Iceland, we shoot south to South Africa – one of the main countries responsible for mining real gem diamonds, alongside Russia and Botswana. Specifically, we’ve come to South Africa’s Premier mine, where the largest rough gem-quality diamond ever discovered was unearthed on January 26, 1905. It was named the Cullinan Diamond after Thomas Cullinan, the mine owner. It weighed 3,106.75 carats (621.35 grams or about 1.37 pounds).

After the jewel was sold to its new owner, the King of England Edward VII, he ordered it to be cut into 9 large diamonds and 96 smaller stones, and 9.5 carats of uncut fragments. Cullinan I and the Cullinan II – the two largest – became part of the Crown Jewels of the United Kingdom – and went a long way to glorifying these natural gems in the public consciousness.

We’ve heard about certain ethical and ecological catastrophes caused by the diamond trade but much of the geology that you think you know about these prized minerals is myth.

Natural diamond nestled in kimberlite

Fodder for inspirational quotes across the World Wide Web, diamonds are beloved and romanticised for their beautiful quality – but also because of a made-up rags to riches geological story.

Most of us bought the lie that diamonds are formed from coal under pressure. In fact, geologists have found most natural diamonds, formed about 100 miles underground billions of years ago, predate even Earth’s first land plants. Consider this: plant matter is the source material of coal, formed 300 to 400 million years ago from the dead remains of vegetation approximately a mere two miles below ground. So, while they might share carbon as their source material, this is where the relationship between diamonds and coal end. Time to return the ring.

So, how are diamonds formed? In the Earth’s mantle, 90 miles (150km) or more beneath the crust, where the pressure is impossible to fathom and the temperatures are at least 2000°F (1050°C) due to the proximity to molten magma, Carbon crystallizes to create diamonds. Geologists have found a number of these Diamond Stability Zones, usually beneath continental plates. In these hot spots, the temperature and pressure are ideal for diamond formation through mineral metamorphosis.

There the diamonds form over billions of years, waiting until an extremely rare event occurs; a deep-source volcanic eruption. These eruptions – never observed by modern humans – explode upwards pushing through Earth’s layers. When the magma cools, it forms igneous rocks known as kimberlites (named after the diamond-bearing region of Kimberly, South Africa), which pipe up through Diamond Stability Zones, bringing xenoliths – or diamond carrying rocks – with them to the surface.

Geologists believe there are three other processes responsible for creating the other diamonds unfit for commercial mining found on earth.

A study indicated blue diamonds containing boron are formed at depths as great as 400 miles (650km) in subducted oceanic crust. Tiny, sub-millimetre diamonds have been found at asteroid crash sites around the world, supporting a theory that the high temperature and pressure of an asteroid colliding with Earth is the third possibility in diamond formation. The fourth is truly out-of-this-world. NASA researchers have found nanodiamonds – measuring billionths of a metre – in meteorites such as Allen Hills. The diamonds here are thought to have formed in much the same manner as at the impact sites of asteroids when meteorites go through high-speed collisions in space before falling to Earth.

5. The World’s Most Active Volcano

As the adage goes, what goes up must come down.

Nowhere is this geological reaction more visceral and terrifying than in the smoking crater of a volcano. While they can be catastrophic and life-threatening, geologists owe volcanic eruptions for the creation of the paradise island chain we know today as Hawaii.

Kilauea Volcano in Hawaii Volcanoes National Park on the Big Island

Here is Kīlauea, the youngest of the Hawaiian volcanoes and one of the most active in the world, so much so that its name means ‘spewing’ in the local language. Since 1952, Kīlauea has erupted 34 times.

In its comparatively short lifespan of between 210,000 and 280,000 years, it has caused much social and ecological unrest with numerous large-scale evacuations, ash clouds and the destruction of Hawaii’s largest natural freshwater lake. In 1790, one such eruption killed more than 400 people, making it the deadliest volcanic eruption in what is now the United States.

Now, looking into its crater, Halema‘uma‘u (literally translated as Fern House), you’ll see into the depths of the 636 feet (194 m) lava lake – a rare phenomenon in its persistence. From up here, you can gaze beyond the dried, cracked, blackened surface to the burning molten magma beneath, popping and fizzing and emanating immense heat. Kīlauea is the body and home of Pele, the Hawaiian goddess of fire, lightning, wind, and volcanoes. Hawaiian oral tradition has told of many eruptions in the past. Now, Pele shares her home with the Hawaiian Volcano Observatory.

In geological terms, like all Hawaiian volcanoes, Kīlauea was created as the Pacific tectonic plate moved over the Hawaiian hotspot in Earth’s underlying mantle. It last erupted on 20th December 2020.

6. The Door to Hell

From fiery heights to burning in the deep, our final stop on this geological highlights tour takes us to one of the least visited countries in the world: Turkmenistan. While it only attracts a few thousand tourists every year, you can bet most of them are here to see the Door to Hell.

Couple looking at the Darwaza gas crater, Turkmenistan

The Door to Hell is named such by the superstitious and those with sensationalist tendencies – although you can see why. To others, it’s a gas crater in Darvaza, measuring about two-thirds of a football field.

This 98-foot-deep gaping hole in the Karakum Desert is believed to have been burning since 1971, for over 40 years, with no signs of being extinguished. To explain why, it’s important to know a little about history, as well as geology.

Once a part of the ancient Silk Road, Turkmenistan fell under Soviet rule for most of the 20th century. The story goes like this: Soviet geologists came to the desert – a natural gas field – to mine for oil but, due to the methane underneath the surface, the ground couldn’t hold the weight of their equipment and gave way. After the collapse, the geologists reportedly decided to burn away the dangerous methane, so set the cavern on fire. They hoped it would only take a couple of weeks, but it’s been burning ever since.

Some local geologists say the crater formed in the 1960s due to a mudflow and didn’t catch fire until the 1980s. Others theorise the Door to Hell – and two other nearby craters full of bubbling mud and water – formed as a result of subterranean water movements under the Karakum Desert.

Only one man, Canadian explorer George Kourounis, has descended into its depths, clad in fire-resistant kevlar kitted out with an internal oxygen supply, to take samples. He found microscopic life thriving in the soil down there, within the toxic gas and temperatures of up to 750°F (400°C).

But it’s not for the faint-hearted. For the brave few who visit and stay firmly above ground, the Door to Hell is sweltering to stand next to – but the temperature plummets once again a few feet back into the dark night of the desert.

It’s a site of extremes – and the end of our journey through the highs and lows of the Earth’s geological offerings. We hope you’ve enjoyed the ride!

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