The geologic time scale (GTS) is a system of chronological
dating that relates geological strata (stratigraphy) to time. It
is used by geologists, paleontologists, and other Earth
scientists to describe the timing and relationships of events
that have occurred during Earth's history.
Bombardment
The Late Heavy Bombardment (abbreviated LHB and also known as the
lunar cataclysm) is an event thought to have occurred approximately 4.1
to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean
and Eoarchean eras on Earth.
Layers of the Earth
The internal structure of the Earth is layered in spherical shells:
an outer silicate solid crust, a highly viscous asthenosphere and
mantle, a liquid outer core that is much less viscous than the
mantle, and a solid inner core.
stratigraphy
Stratigraphy is a branch of geology concerned with the
study of rock layers (strata) and layering
(stratification). It is primarily used in the study of
sedimentary and layered volcanic rocks.