Can you believe it? It was once freezing cold near the equator

Angola, Africa, near the equator, has a tropical savanna climate. What people are most impressed with when they come here is: the hot sun, the empty savanna, the strong ultraviolet rays and the dark-skinned people - it is hot and a little dry. However, in this area that is now very hot, geological surveyors have discovered several hundred meters thick rocks - moraine formed by glaciers 720 million years ago, as if telling us that this place near the equator has experienced extremely cold weather that we can hardly imagine. Thick ice and snow once covered this vast land, leaving behind its long-standing activities.

Ancient glaciers, seabed traces

As time goes by, the world changes dramatically. From about 720 million years ago to 635 million years ago, the Earth experienced the most extreme ice age in its history. The temperature of the entire earth dropped sharply, the climate became cold, the ice sheet spread from the poles to the equator, and the oceans were almost completely frozen. The entire earth turned into a huge snowball, which people called the "Snowball Earth". Most biological populations were ruthlessly ended and buried deep in the dust of history.

When global temperatures rise, seemingly motionless land glaciers will slowly flow from high altitudes to the ocean like squeezing toothpaste, capturing large amounts of rocks at the bottom and on both sides as they go. As the glaciers continue to melt, these debris of varying sizes sink into the ocean basin. After millions or even hundreds of millions of years of solidification, they eventually form the moraine we see in Angola today, which spans the equator, runs parallel to the west coast of Africa, stretches for more than 1,400 kilometers from north to south, and has a cumulative thickness of hundreds of meters.

Extremely cold things, alternative beauty

The special "frozen experience" has created the unique characteristics of tillite: tillite is generally hard and brittle, and the gray-white debris scattered in the dark gray mudstone is like stars in the night sky, which looks mottled and uneven, giving people a different visual experience and special beauty.

When an iceberg wrapped with large gravel floats on the ocean like a ship, as the iceberg melts, the large gravel falls to the bottom of the sea, bending the fine-grained rock layers formed earlier. This phenomenon of fine-grained rock wrapped with large gravel is a common rock fall structure with dynamic beauty in tillite, and is one of the most direct evidences for identifying tillite and glacial sedimentary environment.

The gravels and debris in tillite vary in size and shape and are randomly distributed. There are often scratches, or cracks, pits, and other shapes on the surface of the gravel, and the shapes vary widely, such as iron-shaped, saddle-shaped, etc. This is a typical feature for identifying tillite.

Rare things are valuable, and strange stones have wonderful uses

As a product of special environment, the formation of large-scale tillite is not easy. Faced with the changes of land and sea in geological history, there are even fewer tillites that can be preserved and exposed on the surface. Scarcity makes things valuable. The unique rock characteristics and genetic significance of tillite make it have special application value. Combined with its alternative beauty, tillite can be used to process and produce high-end stone crafts including tourist souvenirs, tea sets, art, gardens, etc., which are of great artistic, collection and economic value.

Scientific exploration, geological secrets

Through the study of moraine, we know that Angola, which is hot and beautiful today, once experienced a long period of "cold" years. From the unique characteristics of moraine and its formation process, we understand the power of ice ages and glaciers, feel the magic of nature, and understand the great changes in the earth's environment during the geological history, which provides an important reference for future research on the earth's climate characteristics and environmental changes.

There are still too many mysteries of nature waiting for people to discover and decipher. Let us continue to explore the secrets of the earth with a scientific attitude, use profound geological knowledge to uncover the mysteries of nature, better maintain our living environment, and protect our home planet.