FORMATION OF EARTH

FORMATION

OF

EARTH

 

For as long as human beings have observed and reflected on the natural world that they inhabit, they have told stories about the formation of Earth. Creation narratives occur in just about every system of belief. They may involve the actions of primeval de ties, abstract powers, or in our modern scientific worldview physical objects and the forces that govern their interactions.

: There is also a human urge to want to date the beginning of the world as we know it.

In the early 17th century, after carefully studying biblical chronolo gies that recounted the span of many kingships and long lists of family descendants, Anglican Archbishop James Ussher announced as a fact that the creation of the Earth had

occurred at 9 a.m. on October 23 in the year 4004 8.c.

Ussher's calculations and their implications were widely accepted for more than a century, but then scien tific study of rock formations and fos sils suggested that Earth had existed longer than Ussher supposed.

We now know that Earth and the rest of our solar system formed

: together about 4.6 billion years ago from a huge cloud of gas and dust fol- lowing a gigantic star explosion within the universe. The sun formed at the center of some debris.

Chunks of matter coalesced into planets, including Earth. In a process known as accretion. Earth's gravity continued (and continues) to attract debris, which becomes incorporated

into its surface. Over time the fledg ling Earth took shape.

Repeated impacts, radiation from the sun, and internal processes caused our planet to settle into layers: an in ner core, an outer core, a mantle, and a crust. A few fragments of the origi nal crust remain.

Interior melting traveled to the surface, creating volcanic processes

that spewed forth lava and gases These gases, including water vapor. gave rise to Earth's primitive atmo sphere. The resulting precipitation ac cumulated over time to form Earth's first oceans.

These materials and processes also set the stage for the appearance of life on planet Earth some 3.5 billion years ago.