地磁场源于地球内部的地核发电机,经由近3000km厚的地幔和地壳到达地面,穿过生物圈、大气层和电离层后延展至太空形成磁层.地磁场对生物圈有双重保护作用:阻挡了高能粒子向内入侵,也避免了氧和水等挥发性物质向外逃逸.尽管地磁场在几十亿年的时间里帮助维持了地球的宜居性,人们仍认为地磁倒转所导致的保护作用削弱会给生物圈带来深刻的负面影响,甚至是生物灭绝.本文梳理地磁倒转与生物灭绝因果关系研究的五十年发展历程,结合历史背景评介早期“一对一”假说的得与失,并着重阐述空间环境变化在最新提出的“多对一”假说中的重要作用.这些研究成果已经清晰地说明,从地核到磁层的地球各圈层是一个耦合的复杂系统,地球演化中的重大事件应当从地球系统科学的角度来看待,并借助比较行星学来研究和理解.
Geomagnetic field originates from the geodynamo inside Earth′s core. It passes through the mantle, crust, biosphere, neutral atmosphere, ionosphere, and then extends into the interplanetary space, and forms a magnetosphere due to interaction with the solar wind. Geomagnetic field can protect the biosphere through two ways. preventing extraterrestrial high energy particles from penetrating inside and confining volatile materials, such as water and atmospheric oxygen, with magnetospheric processes. Geomagnetic field has been thought to play a very important role for retaining the habitability over the Earth′s history; however, a reduction of geomagnetic field could impose some catastrophic consequences on the biosphere, even causes mass extinction. Here we review the investigation of the causal relation between geomagnetic reversal and mass extinction over the past 50 years, and comment on the significance of those earlier works focusing on the "one-to-one" relation by standing on a historical ground. We also introduce the advances of the newly proposed "many-to-one" relation. It has been suggested that Earth′s interior and space environment should be regarded as one system, and some geological events should be understood through a perspective of Earth system science and comparative planetology.