Relive Important Archive Articles

Geologists have been investigating a potential cycle in geological events for a long time. A recent analysis on the ages of 89 well-understood geological events from the past 260 million years show a catastrophic 27.5 million year pulse in eight clusters of world-changing geologic events over geologically small timespans. This pulse of clustered geological events – including volcanic activity, mass extinctions, plate reorganizations, and sea level rises – is incredibly slow, a 27.5-million-year cycle of catastrophic ebbs and flows. As you can see from the graph, some of those times were tough – with over eight of such world-changing events clustering together over geologically small timespans, forming the catastrophic ‘pulse’. “These events include times of marine and non-marine extinctions, major ocean-anoxic events, continental flood-basalt eruptions, sea-level fluctuations, global pulses of intraplate magmatism, and times of changes in seafloor-spreading rates and plate reorganizations,” the team writes in their paper. These cyclic pulses of tectonics and climate change may be the result of geophysical processes related to the dynamics of plate tectonics and mantle plumes, or might alternatively be paced by astronomical cycles associated with the Earth’s motions in the Solar System and the Galaxy. Luckily for us, the research suggests we have another 20 million years before the next ‘pulse’. 

New research reveals the ancient animals survived some 8,000 years later than previously thought Frozen soil samples collected around a decade ago are rewriting our understanding of iconic Ice Age animals like the woolly mammoth. The soil samples were pulled from Canada’s permafrost in the early 2010s, but no work on them had been published until recently. A new analysis of the DNA samples reveals that woolly mammoths, wild horses and steppe bison were around as recently as 5,000 years ago—some 8,000 years later than previously thought, according to a study published this week in Nature Communications. Scientists reconstructed the ancient ecosystem using radiocarbon dating of plant material trapped in the soil in combination with microscopic genomic sequences from animal species. Their results showed something unexpected: Large mammals like mammoths and horses were already on the decline before the climate warmed. The scientists found evidence of woolly mammoth and North American horse DNA as recently as 5,000 years ago, which means the animals held out until the mid-Holocene. Excerpted from the Smithsonian Magazine article by Corryn Wetzel

Spring may have been when a roughly seven-mile-wide asteroid struck the Earth, immediately triggering the mass extinction that would wipe out 76 percent of known species. That key piece of timing doesn’t come from dinosaurs, but from the fish that swam in the waters dinosaurs drank from. By studying the fossil bones of these fish and comparing them to their modern counterparts, Vrije Universiteit Amsterdam paleontologist Melanie During and colleagues have come to the conclusion that the impact that ended the Age of Dinosaurs most likely occurred in the spring. Like their modern counterparts, ancient sturgeons and paddlefish of the Hell Creek Formation, found in the “Tanis” fossil site in North Dakota, grew in cycles. Those researchers proposed that this place contains critical clues about the first minutes and hours of what transpired after impact—including well-preserved fossil fish that contain asteroid impact debris in their gills. During warmer months when food was plentiful, the ancient fish grew and added more bone tissue just as their modern relatives do. During cooler, harsher months, however, their growth slowed and left a line—called a line of arrested growth, or LAG—in their bones. In addition, the bones of these fish contained signatures from oxygen and carbon isotopes. The geochemical signals in these isotopes were influenced by what the fish were eating and the waters they swam in, a natural phenomenon that has been used by paleontologists to study everything from when early whales took to the seas to what plants ancient herbivores ate. Details of the prehistoric sturgeon and paddlefish bones indicate that these fish had not yet hit the peak of their annual growth spurt, which would be expected during the warmest parts of the year. The carbon isotope ratios in the paddlefish bones also match up with this pattern. If these ancient fish lived according to a similar annual cycle as their living relatives, then the signatures in their bones hint that they perished in spring. The fact that tiny spherules thrown into the air during the impact were found in their gills places the time of death within minutes or hours of the end-Cretaceous impact. Together, these lines of evidence suggest that the impact took place while the Northern Hemisphere was in spring and the Southern Hemisphere was still in winter. Read more in the Smithsonian Magazine article by Riley Black that this was taken from, or a Science Alert article that also recaps the paper published in Nature.

Archaeologists have long debated how and when people entered the Americas. Throughout the 20th century, the mainstream hypothesis was that the Clovis people were the first to pass into Alaska about 13,000 years ago.  Stemming from his excavations between 1977 and 1987 at the Bluefish Caves in northwestern Yukon, Jacques Cinq-Mars, a Canadian archaeologist, unearthed evidence that hunters were using the site some 24,000 years ago. Lauriane Bourgeon, a French archaeologist, has spent much of her career re-examining and dating the Bluefish Caves collection to clarify the history of the contentious site. Her research has shown that at least 15 bones from the Bluefish Caves were cut-marked by people as early as 23,500 years ago.