Is the Mystery of Earth's 1.2 Billion Missing Years Solved? | SciShow News

Summary

This video delves into the mystery of the Great Unconformity, a phenomenon where over a billion years of Earth's geological history are missing from the record. Recent research suggests that massive glaciers during the 'Snowball Earth' period eroded and removed vast amounts of rock, which were then recycled into the Earth's mantle. The study also explores the potential connection between this erosion and the Cambrian Explosion, where biodiversity dramatically increased. While further research is needed, these findings offer new insights into Earth's ancient history.

Takeaways

• 🧊 The Great Unconformity is a significant geological mystery where over a billion years of Earth's history is missing from the geologic record.
• 🧗‍♂️ Researchers have proposed that massive glaciers during a period called 'Snowball Earth' may have eroded over a dozen vertical kilometers of rock, contributing to this missing time.
• 📜 The Great Unconformity is characterized by a sudden jump in the age of rock layers, first identified in the Grand Canyon by geologist John Powell.
• 🌍 Geologists have found that around 10 billion cubic kilometers of Earth's crust disappeared, representing nearly a quarter of Earth's history.
• 🔬 By studying zircon crystals, scientists discovered that a significant amount of Earth's land was eroded and recycled into magma during the Snowball Earth period.
• 💎 The presence of these zircon crystals supports the idea that glaciers scoured the Earth around 650 million years ago, depositing the eroded material into the oceans.
• 🧬 The lack of impact craters from before the Cambrian period supports the theory of extensive glacial erosion during Snowball Earth.
• 🔥 One challenge remains in explaining why no new rock layers formed immediately after the glaciers retreated, as Earth's warming occurred before the unconformity ends.
• 🌱 Some researchers suggest that the erosion might have triggered the Snowball Earth conditions, leading to a global glaciation event.
• 🌊 There is a poetic hypothesis that the massive environmental changes during this period could have contributed to the Cambrian Explosion, leading to a dramatic increase in biodiversity.

Q & A

What is 'The Great Unconformity' in geology?

The Great Unconformity refers to places in the geologic record where there is a sudden jump in the aging of rock layers, with a significant amount of time unaccounted for. This phenomenon is marked by missing layers that represent billions of years of Earth's history.

Who first discovered The Great Unconformity, and where?

The Great Unconformity was first discovered by geologist John Powell in 1869 while he was exploring the Grand Canyon. He found that over a billion years of geologic record was missing.

What are the two main hypotheses proposed to explain The Great Unconformity?

The two main hypotheses are: (1) No new sediment was deposited over the missing millennia, or (2) there was massive erosion that removed the geologic record, scraping away the layers of sediment.

How did the researchers study the rocks above and below The Great Unconformity?

Researchers examined the Tapeats Sandstone above the unconformity, which dates to the Cambrian period (about 525 million years ago), and the Vishnu Schist below it, which is over 1.6 billion years old. They looked for clues in the compression of rock layers and the volume of material in the rocks to understand what happened.

What role did zircon crystals play in the researchers' findings?

Zircon crystals were crucial because they survive major geologic processes and capture geochemical conditions when they form. By analyzing isotopes of uranium, oxygen, and hafnium in these crystals, researchers could trace the origin of the material and determine that a significant portion of Earth's land was eroded and subducted into the mantle.

What is 'Snowball Earth,' and how is it related to The Great Unconformity?

'Snowball Earth' refers to a hypothesis that around 650 million years ago, the Earth was completely or mostly covered in ice. The study suggests that massive glaciers during this period were responsible for eroding and removing the missing rock layers, leading to The Great Unconformity.

Why are there fewer impact craters before the Cambrian period compared to after?

The researchers noted that massive ice sheets during the Snowball Earth event likely scraped away shallower craters. This explains why there are many impact sites from the Cambrian period onward but very few from before that time.

What are some unresolved questions about The Great Unconformity?

One unresolved question is why there are no layers from the time when Earth warmed up, after the glaciation ended. Some scientists suggest the erosion occurred before the Snowball Earth event, potentially triggering the global ice age, but more research is needed.

How might The Great Unconformity be connected to the Cambrian Explosion of life?

Some scientists speculate that the environmental changes caused by the massive erosion might have contributed to the Cambrian Explosion, a period of rapid diversification of life. The erosion could have created shallow seas that were rich in minerals, providing fertile grounds for marine life to flourish.

What is the significance of the researchers' findings in the context of Earth's history?

The findings provide a potential explanation for a significant gap in Earth's geologic record and suggest that the harsh conditions of the Snowball Earth event may have played a role in shaping the biodiversity we see today. However, further research is needed to confirm these connections.