Introduction to Earth Science Quiz online

The division of the Earth into the crust, mantle, and core is based on chemical composition (the types of rocks and metals that make up each layer). In contrast, divisions like the lithosphere and asthenosphere are based on physical properties like rigidity and plasticity.

The lithosphere is the cool, rigid outermost shell of Earth, encompassing the crust and the uppermost portion of the mantle. Below it lies the asthenosphere, which is a hotter, weaker, and more ductile layer of the mantle.

Given that the Earth is approximately 4.6 billion years old and modern humans have only existed for a few hundred thousand years, human history represents an incredibly tiny fraction of geologic time. This extremely brief duration equates to roughly 0.005% of the planet's total lifespan.

Scientific consensus, based on radiometric dating of meteorite material and the oldest known Earth and Moon rocks, places the age of the Earth at approximately 4.54 to 4.6 billion years. The other options are either historical years, far too young, or humorous distractors.

In science, a theory is a comprehensive explanation of an aspect of nature that is supported by vast evidence and has withstood rigorous testing. A hypothesis is merely a tentative, untested explanation, while blogs and tweets are informal social media platforms.

The atmosphere is the layer of gases surrounding Earth that contains the oxygen we breathe and shields us from harmful solar radiation. The geosphere refers to the solid Earth, the biosphere includes all living organisms, and the hydrosphere consists of all Earth's water.

Approximately 97% of Earth's total water supply is saline water found in the oceans. Only about 3% is freshwater, and most of that is locked up in glaciers and ice caps, leaving very little accessible liquid freshwater.

A hypothesis is a proposed, tentative explanation for a phenomenon that can be tested through further investigation and experimentation. A theory is a well-tested and widely accepted explanation, while a conclusion is the final decision reached at the end of an investigation.

Earth's system is divided into four major interacting components: the atmosphere (air), geosphere (land/rock), biosphere (life), and hydrosphere (water). The other options contain incorrect, informal, or humorous terms like 'Disneysphere' or list scientific disciplines instead of physical spheres.