During the time the planet was formed, but conditions were unsuitable for life. ; A sample of ice taken from glaciers or other accumulations, often showing seasonal layering.
[den., science] Ice cores can be dated by multiple independent means, with the oldest published date of 140,000 ± 15,000 years for the Vostok core from Antarctica. The other two types of rock are sedimentary, formed by the cementing together of soil or sand, and metamorphic rocks reformed by heat over long periods of time.
Electron-capture decay The only type of radioactive decay that requires the presence of something — an electron — outside the atom's nucleus.
Electron capture decay of light atoms — those having the fewest electrons — can be very slightly affected by extremely high pressures or certain chemical bonds, so as to change their half-lives by a fraction of a percent.
An atom may share electrons with an adjacent atom or atoms; the result being a molecule.
Richardson, professor of geology at Iowa State University (based on the glossary in Earth: An Introduction to Geologic Change, by S. It followed the Hadean, and lasted from around 3.8 to 2.5 billion years ago.
Geologic(al) time scale a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth.
Hadean The oldest eon in the history of the Earth, extending from the origin of the Earth about 4.5 billion years ago to around 3.8 billion years ago.
The term Ediacaran was replaced for a while by Vendian, but now it seems that Ediacaran is back in fashion.
Electron capture Nuclear decay in which a proton in the nucleus acquires an electron from the outer cloud of the atom's electrons.