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Throughout its 4.5 billion-year history, Earth has hosted an array of awe-inspiring geologic formations and remarkable events. Each of these has shaped both the planet and the life forms that followed, leaving us to wonder how different we might be today had these events unfolded differently.
10. Earth: The Blue Planet
Around 71 percent of Earth's rugged outer surface is covered by water, but there's still plenty of dry land left for picture-perfect landscapes. Travel back billions of years, though, and our planet was a true-life Waterworld.
If extraterrestrials had passed through the solar system 2.5 billion years ago, they would have looked down on a dazzling blue sphere. Back then, Earth was almost entirely ocean, with only about 2–3 percent of its surface rising above the water. According to Nicolas Flament from the University of Sydney, this was due to the mantle being 200 degrees Celsius (360 °F) hotter than today, caused by an excess of radioactive materials. These heat sources raised the suboceanic crust, pushing the seas upwards and triggering floods of biblical proportions.
The vast planetary ocean was once thought to be a boiling cauldron with limited minerals, but recent studies from Stanford suggest much more temperate conditions. Earlier estimates ranged from 55–85 degrees Celsius (131–185 °F), enough to melt Earth's early organisms into a hydrocarbon stew. However, isotopic analysis of hydrogen and oxygen in chert, a fine-grained sedimentary rock, reveals that the seas never exceeded a comfortable 40 degrees Celsius (104 °F), perfect hot tub temperature. While the hydrogen might have increased aquatic acidity and posed a risk to early life, much of it escaped into space.
9. Asteroid-Triggered Basaltic Landforms
The asteroid that struck the Yucatan Peninsula 66 million years ago wasn't the only factor in the extinction of the dinosaurs. Following the principle that, 'If you want something done right, do it yourself,' Earth itself delivered the final blow with a surge of volcanic eruptions.
A recent study from UC Berkeley proposes that the asteroid shook Earth like a bell, sending seismic waves across the planet and causing volcanoes to erupt like geological pimples. Along with the impact's immense force, it's believed that molten rock naturally rises through the mantle in frothy plumes every 20–30 million years. These occurrences are linked to several mass extinctions. Geological evidence also shows that earthquakes can trigger volcanic activity, and scientists suggest that the asteroid's impact caused magnitude-9 tremors worldwide.
The most significant eruptions took place in what is now India, releasing massive basaltic flows that created the Deccan Traps. At one point, the lava covered an area the size of California to a depth of 1.6 kilometers (1 mile). Although this region had been active before the impact, the asteroid seems to have intensified volcanic activity in the area, as the magma from before and after the impact differs chemically.
8. Glacial Lake Missoula
During the last ice age, glaciers advanced into the Pacific Northwest, extending into the Idaho panhandle and blocking drainage channels, resulting in the formation of Glacial Lake Missoula, which reached depths of 600 meters (2,000 feet). Holding more water than Lake Erie and Lake Ontario combined behind a creaking ice dam, disaster was inevitable... and absolutely awe-inspiring to witness!
The ice dam, prone to leaking, eventually failed completely between 13,000 and 18,000 years ago. With no barrier to hold back the vast glacial waters, Missoula unleashed two massive lakes’ worth of water across Idaho, Washington, and Oregon. The flood's peak flow was 10 times greater than all of Earth's rivers combined, emptying itself in just a few days.
While the ice sheets have retreated until the next ice age, they’ve left behind a lasting reminder. Parts of the Northwestern US are covered in ripples, much like those formed on beaches by ocean waves. However, these ridges soar up to 15 meters (50 feet) high, created by massive floods that swept across the land at speeds of 80 kilometers per hour (50 mph), rolling the earth like a rug on its way to the sea.
7. Enormous Volcanic Oceanic Ridge
Before complex life emerged, Earth's landmasses were all fused together into a supercontinent known as Rodinia. As Rodinia broke apart and its individual continents drifted, atmospheric carbon dioxide levels began to decrease. Around 700 million years ago, this shift led the planet into a global ice age, famously known as 'Snowball Earth.'
It seems that the disaster which encased our world in ice ultimately preserved it, even fostering the oceans with the nutrients necessary for the diverse array of life that followed. How, you ask? According to research led by Southampton, the breaking up of Rodinia created a vast oceanic ridge stretching thousands of kilometers. This ridge, dotted with volcanoes, enriched the seas with minerals from deep within the Earth's core.
This theory is supported by the presence of cap carbonates—dense, jagged layers formed by ancient volcanic flows. However, such deposits could not have formed unless the ocean was unexpectedly alkaline. It was once speculated that rainfall carried dissolved minerals into the sea, dramatically altering the pH, though this is unlikely to have occurred to such a large extent. Instead, explosive underwater volcanoes showered the oceans with a variety of chemicals, particularly phosphorus, which is vital for building cellular membranes and DNA—the foundational elements of multicellular life.
6. Volcano's Scar Reveals Signs of Ancient Mega-Tsunami
A few hundred miles off Africa's West Coast, the Cape Verde Islands bear traces of an ancient catastrophe. On Santiago, the largest island, home to 250,000 people, researchers discovered something unusual—boulders that seemed out of place. Aside from magic, only a tsunami could have flung 700-ton stones around 800 meters (2,600 feet) inland, hundreds of feet above sea level.
Around 50 kilometers (30 miles) from Santiago, researchers pinpointed the culprit—Fogo, one of Earth's most active island volcanoes. This massive, scarred volcano tells the tale of a cataclysmic event that took place approximately 73,000 years ago, when part of its flank collapsed into the ocean, displacing massive amounts of water and sending catastrophic waves toward the Cape Verde islands.
The tsunami reached a towering height of 170 meters (560 feet), as tall as the Washington Monument. For perspective, the tsunami triggered by earthquakes in the Indian Ocean in 2004 and Japan in 2011 peaked at 40 meters (130 feet). Fortunately, such extreme events are incredibly rare. Researchers speculate (or perhaps hope) that another such catastrophe won’t occur for at least another 100,000 years.
5. The Markagunt Gravity Slide
Utah wasn’t always the arid desert we know today. Around 20–30 million years ago, southwestern Utah was speckled with erupting volcanoes. While these volcanoes are no longer active, they left behind a blanket of ash and igneous material, which now forms the Marysvale volcanic field.
Unexpectedly, geologists discovered broken rocks wedged between the layers of volcanic debris. Initially, they assumed these stones had come from various sources, as rocks typically do. However, it now appears that these fractured boulders were deposited during a singular, massive event—a landslide known as the Markagunt gravity slide.
Regarded as one of the largest landslides in history, it covered an area larger than 39 combined Manhattans. In total, 1,700–2,000 cubic kilometers (400–500 miles) of rock were scattered across 3,400 square kilometers (1,300 square miles) of Utah’s landscape. By analyzing the ash layers above and below the rocks, geologists have estimated that this landslide took place somewhere between 21.6 and 22 million years ago.
The exact cause remains a mystery. It’s possible that rising magma caused a volcano’s flanks to bulge outward, creating an unstable pile of shattered rock. What is known, however, is that the friction generated by the landslide was intense enough to melt the material into glass-like shards, 2–5 centimeters (1–2 inches) thick.
4. The Western Great Lakes
At the height of the last ice age, the Last Glacial Maximum, the western United States boasted its own set of great lakes, as large as today’s Great Lakes. Researchers at Stanford have discovered that these enormous lakes were so massive due to lower evaporation rates.
Spanning vast areas of California, Nevada, Oregon, and Utah, these lakes expanded gradually, sustained by rivers and streams. It was once mistakenly believed that increased rainfall and snowfall were responsible for their size. To study the climate of that time, researchers took samples of tufa, or limestone, from Lake Surprise, a small fossil lake located in Surprise Valley, California. Its dry lakebed is a geological treasure trove, marked by undulating ridges—the remnants of ice age shorelines.
By examining the decay of carbon-14 and uranium, as well as the ratio of oxygen isotopes, scientists determined that evaporation rates were 40 percent lower than they are today due to widespread cooling. They also discovered that Lake Surprise was once as vast as San Francisco Bay, covering an area of 1,010 square kilometers (390 square miles).
3. Saharan Oases
The Sahara Desert, now a mostly barren and inhospitable landscape, was once home to three major rivers—Irharhar, Sahabi, and Kufrah—that cut across the desert 100,000 years ago.
These rivers weren’t just small trickles of water. They carved lush, fertile channels through the now-dry desert. It’s believed that these waterways may have helped early humans as they moved toward more hospitable climates. While the exact path of our ancestors into the Mediterranean remains unclear, researchers now think it may have been along these verdant routes. In addition to these rivers, northeastern Libya was dotted with 70,000 square kilometers (27,000 square miles) of lagoons and wetlands, a vital oasis for both travelers and the small animals our ancestors likely hunted.
In a separate radar survey conducted by a Japanese satellite, a network of ancient waterways was uncovered beneath the sands of Mauritania. This river channel stretched over 500 kilometers (300 miles) through the Western Sahara toward the sea. It last flowed 5,000 years ago, and if it could be revived to its former state, it would rank as the 12th largest river in the world.
2. The Western Interior Seaway
During the early to mid-Cretaceous period, a vast inland sea known as the Western Interior Seaway divided North America. This waterway connected with the Labrador and Hudson Seaways, which encircled Canada and the northern reaches. The Seaway formed as tectonic shifts caused the land to sink, allowing seawater to pour in. It stretched from the Arctic Ocean to the Gulf of Mexico, dominating the landscape.
Irregular tectonic activity caused the inland seas to fluctuate, causing dramatic shifts in their shorelines and leaving behind layers of sand, silt, and clay. Some of these remnants are still visible today, such as the sandstone formations known as the “Rimrocks” in Billings, Montana.
As the landscape evolved during the late Cretaceous, the Seaway gradually withdrew northward, leaving behind expansive alluvial plains that would go on to reveal some of the richest dinosaur fossil sites in North America. Ongoing subduction and the grinding of continental plates eventually led to the creation of a mammoth uplift that formed what we now know as the Rocky Mountains.
1. Massive Ancient Mountain Spurred Life
One of geobiology’s greatest enduring mysteries: Around 600 million years ago, an enigmatic source enriched the oceans with essential molecular building blocks, sparking a rapid proliferation of life forms. Recent studies have pinpointed an unexpected contributor—an ancient mountain range that rivaled the size of the Himalayas.
This range formed when two continental plates collided, forcing huge pieces of the Earth's crust down into the mantle. From this violent clash emerged the largest prehistoric mountain range in the world, along with a vast array of new materials born from the intense heat and pressure of the rocks. The discovery also affirms the existence of landforms comparable in size to the Himalayas in Earth's past.
The mountain range spanned 2,500 kilometers (1,600 mi) across what is now Africa and Brazil, which were once joined as part of the supercontinent Gondwana. Over time, the range suffered extreme erosion—an inevitable fate for massive terrestrial formations—and its mineral wealth poured into the seas. After hundreds of millions of years, the mountains have been reduced to dust, leaving only a web of rocky remnants and a few scattered cacti to mark their once-mighty presence.
