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Geology is the scientific exploration of the Earth’s solid materials and the ongoing processes that shape its surface. Geologists contribute fundamental evidence supporting concepts such as plate tectonics and Earth's biological evolution. In modern applications, geology aids in the discovery of minerals and hydrocarbons, as well as the assessment of water resources. This field also equips scientists with the knowledge needed to predict natural disasters and address recurring environmental concerns.
The Earth’s age is estimated to be about 4.54 billion years. The natural features found across our planet offer geologists, archaeologists, and historians a lens through which they can study past environmental occurrences and their influence on humanity. This article will delve into ten significant geological discoveries that have made an impact in the scientific community, all occurring in the past 15,000 years, a brief period on the geological timescale.
10. Mahuika Crater
In 2003, Dallas Abbott, a member of the Holocene Impact Group, and her team from the Lamont-Doherty Earth Observatory at Columbia University published a paper that pinpointed a submarine crater located on the southern edge of New Zealand's continental shelf, just south of the Snares Islands, about 120 km southwest of Stewart Island. This crater was named the Mahuika crater. The crater measures 20 ± 2 kilometers in diameter and is more than 153 meters (501 feet) deep. Abbott proposed that an impact event occurred around 1443 AD (568 years ago), based on anomalies in elements, fossils, and minerals. However, Edward Bryant’s later research suggested that the impact occurred on February 13, 1491.
Around 1400 AD, the indigenous people of New Zealand abandoned their coastal settlements in the south and migrated inland. During the 15th century, New Zealand experienced numerous volcanic eruptions, including the formation of Rangitoto Island in the Hauraki Gulf near Auckland. By the century’s end, several species of animals, including the flightless moa (eleven species of birds), the giant Haast’s Eagle, and the predatory, flightless Adzebills, went extinct.
Researchers were drawn to the region after discovering large deposits of beach sand located on Stewart Island, at 220 meters (721 feet) above sea level near Hellfire Hut, and 150 meters (492 feet) above sea level at Mason Bay. In eastern Australia, megatsunami deposits with run-up heights of over 130 meters (426 feet) and a C-14 dating to around 1500 AD have been found. Similar megatsunami deposits are located on the eastern side of Lord Howe Island in the Tasman Sea, suggesting the Mahuika crater, located further east, as the likely source.
The largest historical earthquakes have generated tsunamis with maximum run-up heights ranging from 40 to 60 meters (131-196 feet). Abbott and her team suggested that a bolide impact, such as the collision of a large meteorite, asteroid, comet, or other celestial body, would better explain the geological and anthropological evidence than an earthquake. The most significant and widely accepted evidence found at the site consists of natural glass rocks called tektites. Tektites form when an impact melts its target material and ejects molten debris into the atmosphere. The Mahuika tektite field contains tektites in various colors, including orange, light green, and clear, visible in natural light. These tektites have been found as far as 220 km from the crater.
Ted Bryant, a geographer from Wollongong University, believes the tsunami might have reached the coast of New South Wales, where he has found evidence of waves as high as 130 meters that hit around AD 1500. Australian author Gavin Menzies has suggested that a mega-tsunami could have caused the destruction of nearly all but one of the 100 ships he claims were sent by China to circumnavigate the globe in AD 1421. However, New Zealand tsunami expert Dr. James Goff disagrees with these claims, stating that there is no evidence to support such a recent impact event. The discovery of the Mahuika crater remains a subject of controversy.
9. Younger Dryas Impact Theory
The Younger Dryas stadial, also known as the Big Freeze, was a period of extreme cold and drought that began around 10,800 BC (12,811 years ago). The cause of this sudden climate shift has been widely debated. No other climatic change of such size, speed, or scope has been observed since. The Big Freeze transformed the forests of Scandinavia into glacial tundra, caused snow levels in mountains to rise, and led to the disappearance of the North American Clovis culture. This abrupt climatic shift has been linked to the extinction of many Pleistocene megafauna.
A group of geologists argue that the Big Freeze was caused by the collapse of North American ice sheets, while others support the Younger Dryas impact hypothesis. This hypothesis suggests that a large airburst or impact event triggered the cold period. Evidence for this impact includes a charred carbon-rich soil layer discovered at over 50 Clovis-age sites across North America. The layer contains unusual substances such as metallic microspherules, carbon spherules, magnetic spherules, iridium, charcoal, soot, and fullerenes enriched in helium. These materials were found at the base of the 'black mat' of organic material marking the start of the Younger Dryas period.
In January 2009, transmission electron microscopy revealed the presence of nanodiamonds in the Earth’s layer dating back to the time of the Big Freeze. This finding, published in the journal Science, suggests that these diamonds provide strong evidence for a collision with a rare swarm of carbonaceous chondrites or comets at the beginning of the Younger Dryas cold interval. This event likely caused multiple airbursts and potential surface impacts, with devastating effects on plants, animals, and humans in North America. It has been proposed that this impact contributed to the extinction of large North American mammals, including camels, mammoths, the giant short-faced bear, and numerous other species.
The evidence for an impact event in North America has been largely rejected by most geologists and historians. Experts have thoroughly examined the claims and concluded that there was no such impact, particularly because no physical evidence supporting the event has been found. Many of the supposed impact signatures have failed to be verified by independent tests. Out of the twelve original lines of evidence, seven have proven to be non-reproducible. As a result, the hypothesis is no longer regarded as plausible within the scientific community, though it remains a subject of ongoing controversy.
8. Flims Rockslide
The Flims Rockslide is the largest known landslide in the Alps. Its impact is still clearly visible to this day. The slide displaced around 12 km3 (2.9 cu mi) of rock. The starting point of the slide is located at 2,700 meters (8,858 ft) above sea level, north of Flims, at Mount Fil de Cassons. The rock that fell is Mesozoic limestone, including Mergel. The angle of the slide was relatively shallow, ranging from 20 to 25 degrees. The debris from the slide formed a dam on the Vorderrhein River, creating a lake in the Ilanz area. Eventually, the Rhine River cut through the debris field in a region known as Ruinaulta.
Geologist Clemens Augenstein conducted a series of tests at the site. He analyzed sediment embedded in the limestone dust. Using carbon dating, the dust was found to be approximately 10,055 years old (plus or minus 195 years), which places the event around 8000 BCE. A second piece of evidence came from wood found inside the debris, located about 2 miles (3.2 km) upstream of the mouth of the Rabiusa River. The wood was identified as originating from the Fil de Cassons area, and carbon dating confirmed it to be around 10,000 years old.
Following the Flims Rockslide, most of the water drained through the upper part of the debris. This event led to the formation of rivers and lakes, many of which have since been gradually disappearing. One such lake, Caumasee, is situated near Flims in the Grisons, Switzerland. The lake is nestled within a vast forest, and its water level fluctuates due to underground water flow. The landslide forced the Rhine River to carve the Ruinaulta canyon, shaping the surrounding expansive forest. This area is now a sanctuary for wildlife, protected by cliffs hundreds of meters high. Its scenic beauty can be easily accessed via Rhaetian Railways, and the destination is a favorite spot for rafting.
7. Missoula Floods
The Missoula Floods refer to the catastrophic floods that ravaged eastern Washington State and the Columbia River Gorge at the close of the last ice age. Geologist J Harlen Bretz was the first to recognize the significance of these floods in the 1920s, as he studied the unusual erosion features of the Columbia River Plateau. In 1923, Bretz published a paper revealing that the channeled scablands in eastern Washington had been shaped by massive flooding. Around 15,000 years ago, a branch of the Cordilleran ice sheet advanced from Canada into the Idaho panhandle region, where it formed a 2,000-foot (610 m) high ice dam, blocking the Clark Fork River and creating glacial Lake Missoula.
As the water depth in Lake Missoula steadily increased, the pressure at the bottom lowered the freezing point beneath the temperature of the ice dam. This allowed liquid water to seep into cracks in the dam. Once a rupture occurred, an immense flood followed. As the water rushed out of the Columbia River Gorge, it caused a backup near Kalama, Washington. The flooding created temporary lakes at elevations over 400 feet (120 meters), inundating the Willamette Valley and reaching as far as Eugene, Oregon and beyond.
During the floods, the Columbia River's path downstream was obstructed by the Okanogan lobe of the Cordilleran ice sheet, causing the water to flow into Glacial Lake Columbia. This blockage prevented the water from continuing down the Columbia River, forcing it to overflow across the highlands of Eastern Washington. This dramatic event reshaped the landscape, forming the Grand Coulee, Moses Coulee, Channeled Scablands, Dry Falls, Palouse Falls, and other notable features. The ice dam, weakened by these repeated floods, eventually failed under the immense pressure, leading to catastrophic consequences. Over a span of 2,000 to 2,500 years (13,000-15,000 years ago), the failure and subsequent flooding occurred 40-60 times, leaving a permanent imprint on the terrain. The lake-bottom sediments deposited by the Missoula Floods are a primary contributor to the agricultural fertility of the Willamette Valley.
The maximum speed of the floodwaters reached 36 meters per second (130 km/h or 80 mph). J.T. Pardee's studies of the Flathead River canyon led him to estimate that the floodwaters surged at over 45 miles per hour (72 km/h). The flow rate was a staggering nine cubic miles per hour, more than ten times the combined flow of all rivers in the world. At its peak, the discharge was about 1.3 billion gallons per second, approximately 1,000 times the average flow of the Columbia River today. When the flood reached the present location of Portland, Oregon, the water level was still about 400 feet (121 meters) above the normal river stage. The extraordinary force of the flood has led many scientists to suggest that multiple unidentified water sources were involved. The largest known rock carried by the Missoula Floods is located on the Ephrata Fan, near Soap Lake, Washington, as seen in the image.
6. Minoan Eruption
The Minoan eruption of Thera was a monumental volcanic disaster that occurred in the middle of the second millennium BCE. It stands as one of the most significant volcanic events in recorded history. The eruption caused widespread devastation on the island of Thera (also known as Santorini), including the destruction of the Minoan settlement at Akrotiri, as well as severe damage to coastal communities and agricultural areas on Crete. Geological evidence shows that the Thera volcano had been active for hundreds of thousands of years, experiencing numerous eruptions. Each eruption was followed by the collapse of the volcano into a roughly circular caldera that eventually filled with seawater.
The amount of material ejected during the Minoan eruption was estimated to be around 100 km³ (24 cu mi), placing the event at a Volcanic Explosivity Index of 6 or 7. On Santorini, a 60-meter (200 ft) thick layer of white tephra covers the soil, marking the ground level prior to the eruption. This layer consists of three distinct bands, each representing different phases of the eruption, suggesting that the volcano may have provided the local population with several months of warning. Given that no human remains have been discovered at the Akrotiri site, it is likely that the population evacuated before the eruption’s catastrophic final phase.
The Minoan eruption dramatically altered the landscape, leaving behind a thick layer of pumice sediments. In certain areas, the coastline was submerged under layers of tuff, while in others, the coastline extended further into the sea. The eruption sent a towering ash plume reaching 30 to 35 km (19 to 22 mi) into the stratosphere. Additionally, when the magma interacted with the shallow marine environment, it triggered a violent steam explosion. This event generated a massive tsunami, 35 to 150 meters (115 to 490 ft) high, which wreaked havoc along the northern coast of Crete, located 110 km (68 mi) away.
One way to determine the timing of the Minoan eruption was through tree-ring analysis. Research has shown that a significant environmental event disrupted tree growth in North America around 1629–1628 BCE (approximately 3,639 years ago). Growth disturbances were observed in European oaks in Ireland and Sweden, bristlecone pines in California, bog oaks in England, and other trees in Germany. Additionally, crop failures in China have been linked to this period. The eruption destroyed the Minoan settlement at Akrotiri, burying it beneath pumice. The event has also influenced Greek mythology and may have led to unrest in Egypt. However, the exact date of the eruption remains a topic of ongoing debate.
5. Burckle Crater
The Holocene Impact Working Group, a collective of scientists from Australia, France, Ireland, Russia, and the USA, proposes that meteorite impacts on Earth occur more frequently than once thought. By analyzing satellite imagery, the group identifies landforms such as chevrons—wedge-shaped sediment deposits—that are believed to be the result of megatsunamis. These chevrons often align with specific impact craters, suggesting that large tsunamis, triggered by meteorite impacts, deposited these features around the globe.
The Holocene Impact Working Group, in their search for substantial chevrons, identified the Burckle crater, an undersea crater located to the east of Madagascar and to the west of Western Australia, in the southern Indian Ocean. The crater’s location was pinpointed in 2006 through evidence from ancient chevron dune formations found in Australia and Madagascar, which enabled the team to triangulate its precise coordinates.
The team used the Fenambosy Chevron—a chevron-shaped landform on the southwest coast of Madagascar, standing 180 meters (590 feet) high and stretching 5 km inland. Situated around 900 miles southeast of the Fenambosy Chevron, the Burckle crater is approximately 30 km (18 mi) in diameter, lying at a depth of 12,500 feet (3,800 m) below the ocean’s surface. Core samples from the Fenambosy Chevron reveal high concentrations of nickel and magnetic elements, which are typically associated with impact ejecta.
Although the crater has not yet been dated through radiometric analysis, the Holocene Impact Working Group suggests that it formed approximately 5,000 years ago (around 2800–3000 BC) during the Holocene epoch. Near the crater, there have been reports of unusual metals, including carbonate crystals, translucent carbon spherules, and fragments of mineral glass. Several ancient cultures refer to a 'great flood' in their writings, and some believe these myths could be linked to the impact event. This time in history saw the end of the Early Harappan Ravi Phase, the fall of the pre-dynastic rulers of Sumer, and the beginning of the First Dynasty of Kish.
4. Tartessos
Tartessos was a port city and the surrounding civilization located on the southern coast of the Iberian Peninsula, in modern Andalusia, Spain, near the Guadalquivir River's mouth. The city appears in Greek historical records beginning in the middle of the first millennium BC. The name Tartessos gradually fell out of use around 2000 years ago. Some historians propose that the city may have been lost due to a sudden flooding event. Numerous discoveries in the region have helped us piece together the story of the Tartessian culture.
The Tartessians were known for their wealth in metals. In the 4th century BC, the historian Ephorus wrote about 'a very prosperous market called Tartessos,' where tin was transported via river, along with gold and copper sourced from Celtic lands. The Tartessians became key trading partners of the Phoenicians. Pausanias, writing in the 2nd century AD, provided a description of the city’s location. He noted that Tartessos (once known as Baetis) was a river in the Iberian land, flowing into the sea through two mouths. Between these mouths lay the city of the same name. The Baetis, known today as the Guadalquivir, suggests that the site of Tartessos may have been lost and buried beneath shifting wetlands.
The region surrounding the Guadalquivir River holds notable geological importance. The delta of the Guadalquivir River has gradually become obstructed by a sandbar stretching from the mouth of the Rio Tinto, near Palos de la Frontera, to the riverbank opposite Sanlúcar de Barrameda. This area is now protected as part of Doñana National Park, which was designated a UNESCO World Heritage Site in 1994. The park has also been recognized as a Biosphere Reserve by UNESCO. Known for its unique biodiversity, Doñana is a wetland of international importance. It supports a wide range of ecosystems and serves as a habitat for thousands of migratory birds from Europe and Africa, as well as fallow deer, Spanish red deer, wild boar, European badger, Egyptian mongoose, and endangered species like the Spanish Imperial Eagle and Iberian Lynx.
In September 1923, archaeologists uncovered a Phoenician necropolis (burial ground) at the site, revealing human remains. Alongside these discoveries, a large collection of artifacts from the South-Western Iberian Bronze culture was unearthed. This culture is known for individual burials, where the deceased was often accompanied by a bronze knife. Many Tartessic artifacts linked to the Tartessos culture have been found, leading many archaeologists to associate the 'lost' city with Huelva, Spain.
Tartessos has long been linked to the myth of Atlantis. Both societies were thought to be advanced civilizations that vanished when their cities were submerged under the sea. In 2011, Richard Freund led a team that claimed to have found compelling evidence pointing to the location of Atlantis in Doñana National Park, based on underground and underwater surveys. However, Spanish scientists have rejected these claims. Additionally, some biblical archaeologists associate the place named Tarshish in the Hebrew Bible with Tartessos.
3. Bridge of the Gods
The Bridge of the Gods is a natural rock formation created by the Bonneville slide, a significant landslide that occurred near Cascade Locks, Oregon, in the Pacific Northwest of the United States. This event, which dammed the Columbia River, is remembered in local Native American legends as the Bridge of the Gods.
The Bonneville landslide sent a massive amount of debris from Table Mountain and Greenleaf Peak, covering an area of over 5.5 square miles (14 km²). This debris fell into the Columbia Gorge near Cascade Locks, Oregon, forming a natural dam across the Columbia River, approximately 200 feet (61 m) high and miles (5.6 km) long. The dam created a lake, flooding a forest of trees for about 35 miles (56 km). Eventually, the river broke through the dam, washing away most of the debris and creating the Cascade Rapids. Geologists have identified that debris from several landslides in the area overlapped, contributing to the Cascades landslide complex, with the Bonneville landslide being the most recent and likely the largest of these events.
The Cascadia fault is a subduction zone stretching from northern Vancouver Island to northern California, marking the boundary between the Juan de Fuca and North American plates. The geological record of the Pacific Northwest shows that significant earthquakes occur in this region roughly every 500 years, typically accompanied by tsunamis. Evidence suggests that at least 13 major seismic events have taken place, with intervals ranging from 300 to 900 years and an average of 590 years. The Cascadia fault is believed to be responsible for triggering the massive Cascades landslide complex.
On January 26, 1700, a massive megathrust earthquake, with a magnitude between 8.7 and 9.2, occurred along the Cascadia subduction zone. Geologist Brian Atwater documented this event in his 2005 book, The Orphan Tsunami of 1700. Atwater has dedicated much of his career to researching the possibility of large earthquakes and tsunamis in the Pacific Northwest. The earthquake generated a tsunami so powerful that it was recorded in Japan, allowing Atwater to determine the precise date and approximate magnitude of the event.
After examining the coastline across the Pacific Northwest, Atwater found evidence of a massive tsunami that struck the area around 1700. The evidence supports the earthquake's severity, including a significant drop in the elevation of coastal lands, as seen in buried marsh and forest soils beneath tidal sediments. Atwater’s team discovered a layer of tsunami sand in the subsided landscape. One of the key clues linking the Japanese tsunami to the Pacific Northwest earthquake comes from tree ring analysis, showing that red cedar trees, killed by the sinking of coastal forests into the tidal zone, had outer growth rings formed in 1699, just before the tsunami struck.
Recent findings suggest that the Cascadia subduction zone is far more complex and volatile than previously understood. Geologists now estimate a 37 percent chance of a magnitude 8.2+ earthquake in the next 50 years, and a 10 to 15 percent likelihood that the entire subduction zone will rupture, causing a magnitude 9+ event within the same timeframe. Furthermore, experts have determined that the Pacific Northwest is not adequately prepared for such a colossal earthquake. If such an event occurs, the tsunami it generates could reach heights of 80 to 100 feet (24 to 30 meters).
The exact timing of the Bonneville landslide remains a topic of debate among researchers. Some propose a date around 1450, while others suggest it occurred around 1700, potentially linking the landslide to the Cascadia earthquake of that year. Native American legends from the Klickitat tribe describe an earthquake so powerful that a large bridge collapsed into the river, resulting in the creation of the Cascades Rapids in the Columbia River Gorge. These legends are believed to date back to the early 18th century.
2. Storegga Slide
The three Storegga slides are regarded as some of the largest landslides known to man. These massive events took place in the Norwegian Sea, off the edge of Norway’s continental shelf, approximately 100 km northwest of the Møre coast. The slides generated an enormous tsunami in the North Atlantic Ocean. Carbon dating of plant material found in sediment deposits indicates that the most recent event occurred around 6100 BC (8111 years ago). Traces of the tsunami have been discovered in Scotland, with sediment deposits found as far as 80 km inland and up to 4 meters above the current tide levels, particularly in Montrose Basin and the Firth of Forth.
The Storegga slides have been extensively studied in relation to the development of the Ormen Lange natural gas field, situated on the Norwegian continental shelf. Research indicates that the slides were likely triggered by a significant earthquake, combined with the release of gases from decomposing gas hydrates. One theory, made public in 2004, suggests that the slide was caused by material accumulated during the last ice age, and that another slide could only occur after a future ice age. If another slide were to occur, it would generate a massive tsunami, potentially devastating the North Sea and Norwegian Sea coasts.
Around the time of the last Storegga slide, geologists identified the existence of a land bridge known as Doggerland. This landmass connected Great Britain to Denmark and the Netherlands, spanning what is now the southern North Sea. Geological surveys indicate that Doggerland was a vast expanse of dry land stretching from the east coast of Britain to what is now the coast of the Netherlands and the western coasts of Germany and Denmark. The concept of Doggerland was first discussed in the early 20th century but gained widespread attention in 1931 when a commercial trawler began to recover remains of land mammals, including mammoths and lions, as well as ancient tools and weapons.
Doggerland is thought to have been a landmass that featured lagoons, marshes, mudflats, and beaches, making it a rich hunting ground for Mesolithic human cultures. Over time, this area was gradually submerged due to a rise in sea levels. It is believed that coastal regions of both Britain and mainland Europe were engulfed by the tsunami triggered by the Storegga slide. This catastrophic event would have greatly affected the Mesolithic population, separating British and mainland European cultures. One area of Doggerland, said to have been wiped out by the Storegga slide, is Viking Bergen, an island located between modern Shetland and Norway, at the intersection of the North Sea and Norwegian Sea.
1. Flooding of the Black Sea
The Black Sea is an inland body of water bordered by Europe, Anatolia, and the Caucasus, connected to the Atlantic Ocean via the Mediterranean and Aegean Seas. Following the last ice age, water levels in both the Black Sea and the Aegean Sea rose independently, eventually reaching a point where water began to flow between them. Originally a land-locked freshwater lake, the Black Sea was flooded with saltwater during the Holocene, which effectively smothered the freshwater below, depriving the deep waters of oxygen. This process created a meromictic body of water, an underwater environment hostile to many organisms that typically decompose wood in oxygenated waters, making it an ideal location for deep water archaeological exploration.
In a series of expeditions led by marine archaeologist Robert Ballard, a team discovered what seemed to be ancient shorelines, freshwater snail shells, and submerged river valleys at depths of around 300 feet (100 meters) off the coast of modern Turkey in the Black Sea. Radiocarbon dating of freshwater mollusk remains suggested an age of approximately 7,500 years. The team also uncovered three ancient wrecks to the west of the town of Sinop, at depths of 100 meters. A report in New Scientist magazine revealed that the archaeologists found an underwater delta south of the Bosporus and evidence of a strong freshwater outflow from the Black Sea dating back to the 8th millennium BC.
The evidence has contributed to supporting the Black Sea deluge theory. In 1997, William Ryan and Walter Pitman from Columbia University proposed a hypothesis that described a massive flood through the Bosphorus (strait) in ancient times. They suggested that the Black and Caspian Seas were once large freshwater lakes, but around 5600 BC (7611 years ago), the Mediterranean Sea overflowed a rocky sill at the Bosphorus, linking the Black and Mediterranean Seas. This event is said to have inundated 155,000 km2 (60,000 sq mi) of land and greatly expanded the shoreline of the Black Sea to the north and west. The researchers claim, “Ten cubic miles (42 km3) of water poured through each day.”
It is widely agreed upon within the scientific community that floods of this nature did occur, and similar events have been recorded in the post-glacial period. However, there is ongoing debate regarding the abruptness and scale of the water shift. Both supporting and opposing publications on the Black Sea deluge theory have emerged, and archaeologists continue to discuss the hypothesis. The claims have led some to link this catastrophe to ancient flood myths. The oscillating hypothesis posits that over the past 30,000 years, water has flowed back and forth between the Black Sea and the Aegean Sea in smaller, intermittent amounts, without predicting any sudden ‘refilling’ events.
