PSES Core Concepts – Earth History

by | Jul 13, 2023 | Uncategorized

Core Concepts — Earth History

1.2a.  The Universe is vast and estimated to be over 10 billions years old.  The current theory is that the Universe was created from an explosion called the Big Bang.  Evidence for this theory includes cosmic background radiation and a red-shift (Doppler effect) in the light from very distant galaxies.

1.2c.  Our solar system formed about 5 billion years ago from a giant cloud of gas and debris.

1.2e.  Earth’s early atmosphere formed as a result of the outgassing of water vapor, carbon dioxide, nitrogen, and lesser amounts of other gases from the interior.

1.2f.  Earth’s oceans formed as a result of precipitationover millions of years.  The presence of an early ocean is indicated by sedimentary rocks of marine origin dating back about 4 billion years.

1.2h.  The evolution of life caused dramatic changes in the composition of Earth’s atmosphere.  Free oxygen did not form in the atmosphere until photosynthetic plantsevolved.

1.2j.  The pattern of evolution of life-forms on Earth is at least partially preserved in the rock record.  Fossil evidence indicates that a wide variety of life-forms have existed in the past and that most of these forms have become extinct. Human existence has been very brief compared to the expanse of geologic time.

1.2j.  Geologic history can be reconstructed by observing sequences of rock types and fossils to correlate bedrock at various locations.

> Geologists have divided Earth history into time units based upon the fossil record.

> Fossils preserved in rocks provide information about past environmental conditions.

> Age relationships among bodies of rocks can be determined using principles of original horizontality, superposition, inclusions, cross-cutting relationships, contact metamorphism, and unconformities.  The presence of volcanic ash layers, index fossils and meteoritic debris can provide additional information.

2.1o.  Plate motions have resulted in global changes in geography, climate, and the patterns of organic evolution.