5 billion years ago, and the earth as a planet also has a history of 4.6 billion years. The time when humans appeared was too far from the time when the earth was born. The history of the earth we know is inferred through geological structures. It is known that the age of the oldest rock on the earth is 4.374 billion years , and the area of distribution is quite small. In geological exploration, scientists found that about 1 billion years of geological strata have disappeared, which means that the history of this period has been miraculously lost.
If you want to explore history, you can run outside and start digging now. You will first find music tapes from the 90s, and next you will dig up the light balls of the disco balls in the 70s, but in the end maybe you will dig out some ancient coins and various other artifacts. So why have human civilization and natural relics sunk to the ground over time?
Because the earth's surface is constantly scattered with fine particles like sand and dust, these particles accumulate in a slow process, which is called deposition. Then another process is called cementation, these mineral particles gradually bond together until millions of years later, sedimentary rock forms, and then another layer of rock forms on that, then layer after layer, cycle through to the ground under your feet.
In all these deposition and cementation processes, animals and plants also die like they are now. After the death of animals and plants, all the soft parts are eaten or rotted, but sometimes the hard parts, such as bones, shells and fruit shells, are slowly covered and deposited by dust. Therefore, as time passes, it is wrapped in the rock, and is constantly chemically changing due to thermal energy and pressure, and more sediments accumulate on the seabed and press down on the rock formation below. As these are wrapped between the upper and lower sedimentary layers, the composition will further change, thus forming fossils. Much of our understanding of the history of the Earth and life itself comes from the study of sedimentary rock strata sequences and the study of fossils.
We call sedimentary rock strata sequences, they are clear and unique, each layer reveals the uniqueness of the age in which it was formed. In hierarchical sequence law shows that if not disturbed, the lower the rock strata, the older it is. It means that, usually when you look at the cross-section of the geological structure, you get a clearer image of the passage of time, but unfortunately, history is not so predictable. Because when new sedimentary rock formations form in one place, if other conditions change, sedimentation stops, wind and water erosion moves particles elsewhere, and a portion of the geological record will be deleted after a period of time. Then the deposition may resume at that location, but these temporary interruptions will leave a gap in the record forever, potentially for millions of years. It's like rewinding the tape and washing the tape, and recording it again, then in the last tape, the missing part is irrecoverable, and if the lost record is quite important, then the tape no longer has its original value.
is composed of the light gray underlying rock shown in the picture above, which is composed of deep-sea sediments about 425 million years ago. But the red upper layer was deposited by rivers and streams about 345 million years ago, with a gap of about 80 million years in the middle. It is based on this discovery that James Hutton published the paper "Earth theory, or the study of the laws of land composition, disintegration and restoration" . However, the most unusual discontinuity was discovered in 1869. John Wesley Powell observed a strange hill while crossing the Grand Canyon. He noticed a vertical rock formation, which should have been three kilometers thick, but after actual measurement, it was found that it was only 150 meters, which was more than 2,000 meters missing. In other words, the geological history here was missing for a long time. Powell named this strange phenomenon, called the large-angle unconsolidation of the stratigraphic .
Nowadays, geologists have been able to determine the age of rocks using radioactive element dating method. They found that Powell's speculation was correct. The crystalline rock he observed was indeed very old. The youngest part was almost 1.7 billion years old, while the red sandstone layer was very young. The oldest part was only 550 million years old, 17:5.5, which means that the rock layer that was more than one billion years short of . What makes geologists even more crazy is that this large-scale unconsolidation phenomenon not only exists in Grand Canyon , but is spread all over the world.
So where did these missing rock formations go? What exactly happened here? Some people have proposed a theory to explain this phenomenon, called the Snowball Earth Theory, which refers to the low temperature period around 1.8 to 550 million years ago. People believe that the surface of the earth was covered by glaciers, just like a huge snowball, which could cause large-scale erosion when moving. It is estimated that they can wash away rock layers of 3-5 kilometers on the surface, which is enough to cover a strata that lasts up to 1 billion years.
is the Cambrian period about 542 million years ago to 490 million years ago. It happened to be a big explosion in life during this period. The fossil record of shows that there is a phenomenon, that is, most animal species have concentrated during this period. The rock layers that were washed away by glaciers before may contain the secret of the origin of life and just happened to be the catalyst for this great explosion of life.
Of course, this is just an imaginary after all. Science and technology are progressing rapidly now. Perhaps one day new technologies can shake the geological world and truly recover those lost history. Then I think this period of history will definitely be very exciting.
