The Terrestrial Causes of the Mass Extinctions

Introduction

The book “Origin and evolution of Earth: research questions for a changing planet” published in 2008 was written by Committee on Grand Research Questions in the Solid-Earth Sciences. It is a study report providing the brief introduction to the Earth science, concluding current founding and discoveries and indicating the expectation of the future research. To generally cover the important topics of the solid-Earth science, the book divides 10 research questions into four parts, namely the origins, the Earth’s interior, the interaction between life and the Earth and the hazards and resources on the Earth.

The reason why a great effort is needed to pay on these questions is that they are significant for understanding the Earth’s history and operation, highly related to sustaining life. Knowing about how the Earth will change in the future is important to human survival. Although the Earth science has made a great progress with advanced technology and scientists’ devotion, increasing discoveries arouse new confusion. As a result, the further research is required to enhance the understanding of the Earth in order to prevent catastrophe and maintain life.

This article will indicate and discuss the importance of each research questions in the book first. Then, it will focus on the mass extinctions because recognizing the what precipitated the disappearance of large quantities of species may help people escape from extinction. The latest findings of the causes of this biological upheaval, the detailed impacts of those causes and the relationship of several causes will be further discussed. At the end, a conclusion will be delivered to summarize the whole article.

Part I

Origins

Enhancing the understanding of humankind’s origin is one of the motivative factors of observing the Earth and the origins of the Earth and other planets is the key to achieving this purpose. According to the astronomical observations of a certain domain, the Sun was formed by the collapse of a molecular cloud core. For giant planets, they start with solid objects and then attract gas. When they accumulate heavier elements, the dense central cores are formed. The Earth’s unique chemical composition making life sustainable may be a result of meteorites from the asteroid belt region, the origins of the Earth’s carbon and water. No geological record of the duration after the Moon’s formation is found and it is urgent to fill this gap. For the origin of life, the result of the top-down approaches supposes that it may begin with nonorganic objects. With the unstable and tough conditions of the early Earth, life may also have emerged many times. Because of great difficulties to simulate the primitive Earth conditions, the actual process of the emergence of life has not reached a common agreement.

The Earth’s interior

The Earth’s evolution is based on the interplay of the inner and outer planet, especially the Earth’s interior providing the major energy and affecting the Earth’s surface critically. The mantle convection is essential for life. According to scientists’ founding, the Earth can heat up by active convection and convect slowly to decline the rate of heat loss when the temperature is dropping. This contributes to the Earth’s thermal evolution. Besides, this is related to the volcanic eruptions and plate tectonics which affect the surface. Learning about rocks can help understand the pressure and temperature they suffered and the geological processes the Earth have gone through. The consequence of the rocks’ deformation is thermal weakening and damage weakening, which provides an evidence that materials properties are important for the Earth’s process.

The Interaction between Life and the Earth

The Earth’s surface conditions have changed from time to time while staying relatively stable and habitable. Climate change is commonly discussed nowadays. Except for the anthropic causes, the climate system is governed by the amount of energy the Earth absorbs from the Sun, which depends on the albedo of Earth’s atmosphere and surface. The reasons for climate change are excessive fossil fuel burning, change in atmospheric particulate and clouds, Earth’s orbital cycles and the tectonic processes. A climate suitable for life is considered to be a result of volcanic emissions of carbon dioxide, weathering of rocks absorbing CO2 and other processes. Obviously, the Earth’s condition greatly affects the evolution of life. Living creature have affected the Earth continuously. The respiration and photosynthesis are essential parts of the Earth’s carbon cycle, critically influencing the climate.

Hazards and Resource on the Earth

Geological processes affect the survival of the human population from the aspects of nutrition and safety. To minimize the loss of catastrophic events, such as earthquakes, tsunamis and volcano eruptions, expanding knowledge are demanded to forecast the geological movement. According to the long-term predictions, where these events may happen may precisely predict but when and in what extent are still difficult to forecast. Fluid flow and transport also affect human environment significantly. In certain cases, the fluid flow could be confined to fractures which are volcanic rocks, a kind of geological media. It can also dissolve or precipitate minerals, which affects the Earth’s surface.

Among the abovementioned research questions, how the Earth and life have shaped each other is significant to humankind and even the whole ecosphere. In next part, the article would focus on this topic.

Part II

The current states of life and the Earth attributes to their interplay between each other. Compared with the life’s impact on the Earth, the organisms may suffer more from the Earth’s changes since they may heavily depend on a favorable environment. The