Why is it said that “land, sea and air” are all inseparable from geology?

On June 21, 2024, Gao Jianwei, senior engineer of the Natural Resources Physical Geological Data Center of the China Geological Survey, gave a speech entitled "Studying geology means living in the mountains?" at the "It's time to serve the country with science" theme session of the Science Popularization China Starry Sky Forum.

The following is an excerpt from Gao Jianwei’s speech:

Traditional geology studies the Earth on which we depend for survival, and only the surface of the Earth, including the shallow part of the crust and our hydrosphere, lithosphere, biosphere and other external spheres.

Now, with the continuous advancement of science and technology, our research objects are also gradually expanding, mainly in three directions: going up to the sky, going into the ground, and going into the sea, which correspond to our deep earth, deep sea and deep space respectively.

Two major tasks of geology

Our geology has two main tasks. The first is to meet the needs of human survival and development, and the second is to explore the unknown of mankind.

Geology has two main tasks. The first is to meet the needs of human survival and development, and the second is to explore the unknown of human beings.

First of all, in terms of meeting the needs of human survival and development, there are several things that need to be done: the first and most important one is to guide people in finding mineral resources; the second is to guide urban construction; the third is to resist natural disasters; and the fourth is to study the geological environment to protect human health.

Another major mission is to explore the unknown of mankind, mainly in three directions: deep sea, deep earth and deep space.

The first is deep space. We can now use high-tech means to conduct geological research on planets in the solar system and explore the unknown of the universe.

The second is the deep sea. We also use high-tech means, such as submersibles, to conduct deep-sea exploration and understand the unknown secrets of the ocean.

The third is deep earth exploration. There are still many unsolved mysteries in geology, such as the origin of life on Earth, the causes of the five mass extinction events in Earth's history, and what the Moho surface between the Earth's crust and mantle looks like. We want to explore these questions, so we need to carry out deep earth exploration.

Geological mysteries in the ocean

There are three ways to go into the deep sea. The first is through a submersible, which we can sit in to explore the deep seabed directly; the second is through a geophysical exploration ship, which uses geophysical methods to understand the interior of the ocean; the third is an ocean drilling ship, such as the "Dream" ocean drilling ship in the picture, which was just built by the China Geological Survey. It is designed to drill in the deep sea, drill a hole on the seabed, and bring up rocks from the deep ocean for our research.

There are many mysteries in the deep sea, such as the trilogy of plate tectonics theory, which includes the theory of continental drift, the theory of seafloor spreading and the theory of plate tectonics.

Initially, Wegener proposed the theory of continental drift. He was lying on his sickbed when he discovered that many continents on the map could be put together. He wondered if these continents were originally together and then became what they are today under the action of some force. He looked for a lot of evidence, including evidence from paleontological fossils, evidence from glaciers, and evidence from structures, and then proposed the theory of continental drift.

After proposing the theory of continental drift, Wegener was questioned by many people. Why? Because he did not solve a problem: what kind of force could cause a complete piece of land to break up into its current state? He failed to solve this problem.

With the advancement of science and technology, this question has been answered in the ocean.

First, Harry Hess used sonar technology to draw a seafloor topography map and discovered that there was a mid-ocean ridge deep in the ocean. After that, people drilled a lot of drills on both sides of the mid-ocean ridge and drilled rock samples, which were basalts. Later, people used isotope technology to determine the age of this basalt and found a very interesting phenomenon: the age of the basalt on both sides of the mid-ocean was gradually getting older, which proved the seafloor spreading theory. The seafloor spreading theory believes that there is a lot of mantle convection at the mid-ocean ridge. The mid-ocean ridge is a place where magma rises. After the magma rises, this driving force drives the ocean to disperse, and the oceanic crust on both sides begins to move to both sides. In other words, the answer to the "driving force" problem that Wegener failed to solve was found in the deep ocean.

Later, geologists proposed the theory of plate tectonics, which holds that the entire earth is divided into six major plates, and that some of the plates converge and some diverge. When they converge, they collide to form mountains and change the world; when they diverge, the continents break apart and the seawater converges to form the ocean, and the cycle repeats. This is a very important result obtained from the ocean.

What does deep space exploration have to do with geologists?

With the development of various high-tech means such as spacecraft, geology has also begun to conduct partial exploration of deep space.

Staff members take out lunar soil samples from the Chang'e 5 return capsule

For example, two years ago, Chang'e 5 brought back a batch of lunar soil samples, and many important results were produced through the study of these samples.

For example, before, by studying the samples brought back by Apollo, foreign geologists believed that the moon had no magma activity 3 billion years ago and had become a dead planet. However, Chinese geologists analyzed and tested the collected lunar basalt samples and believed that the moon still had magma activity about 2 billion years ago. This is a major breakthrough and discovery.

Heading deep into the Earth

Deep earth means advancing into the depths of the earth and conducting deep exploration.

We have two means.

One is the geophysical method, which is a relatively indirect method. Simply put, geophysics is the use of geophysical methods to explore the structure of the earth's interior, including various anomalies. Its main methods include gravity, magnetism, electricity, earthquakes, etc.

For example, geologists can use earthquakes to study the structure of the Earth. By receiving the seismic wave speed of some large earthquakes on Earth, geologists divide the Earth into three layers: the crust, mantle and core. Later, geologists proposed that the interior of the Earth is not all rigid, not all stone, but there is a layer of asthenosphere in the upper mantle, which is a bit like the pimple soup we eat, which is a kind of asthenosphere that can flow but is not entirely liquid.

The second method is scientific drilling, which is a more direct method. To put it simply, it is to dig a hole deep underground from the surface, as deep as possible. The deepest scientific drilling well in the world is located on the Kola Peninsula, with a depth of more than 12,000 meters.

In 1996, the international community established a "Continental Scientific Drilling Program". Under this scientific drilling program, China has successively drilled three scientific drilling wells, namely the Continental Scientific Drilling Well in the East China Sea, the Continental Scientific Drilling Well in Qinghai Lake, and the Scientific Drilling Well in the Songliao Basin.

At present, the deepest well drilled in China is not among the three wells mentioned above, but the Taco 1 well that is still under construction. It is still under construction and the depth has reached more than 10,000 meters.

Construction site of Taco 1 well

In addition, there is the Songke 2 well in the Songliao Basin, which has been drilled to a depth of 7,018 meters. Why was this Songke 2 well drilled? There are two purposes.

First, let’s see if there are any oil and gas resources deep in the Songliao Basin. Since oil is a non-renewable resource, we need to seek resources from deep within the earth.

Second, restore the Earth’s climate. There is a method in geology called “using the present to discuss the past”, and another method called “using the past to discuss the present and the future” - this one belongs to “using the past to discuss the present and the future”, by studying the ancient environment and ancient climate of the Songliao Basin, predicting the current and even future climate changes of the Earth.

The rock cores obtained from Songke No. 2 Well are extremely precious. At a depth of more than 7,000 meters, geologists have conducted analytical tests on every layer and every centimeter of the rock core, restoring the ancient environment and climate of the Songliao Basin at that time, and providing new evidence of asteroid extinction.

What is the new evidence?

Traditionally, it is believed that the cause of dinosaur extinction was an asteroid impact. However, through research on the Songke Well 2, Chinese geologists believe that before the asteroid impact, the environment and climate in the Songliao Basin were already very bad. At that time, the concentration of carbon dioxide in the air was very high, and some organisms had died or become extinct. Then, at the end of the Cretaceous period, after the asteroid impact, a large number of organisms died and became extinct. Therefore, scientists now believe that the extinction of dinosaurs was caused by multiple factors, and that the combined effects of volcanoes and asteroid impacts led to the further extinction of dinosaurs.

Author: Gao Jianwei, science writer, senior engineer of the Natural Resources Physical Geological Data Center of the China Geological Survey