Stufy
Earth History (Geological Timeline)
Lecturer Dr. Sameh Abu El Soud
History of Early Geology
Catastro‐phism Tries to explain the presence of everything on earth and their composition by catastrophes. E.g. A catastrophe happened to dinosaurs 80 million years ago. A comet fell on earth surface leading to volcanoes, leading to dust clouds in the atmosphere, preventing solar rays penetration , the plants died and then the dinosaurs.
Uniformi‐tarianism (James Hu on, late 1700s) ‐ He proposed that the same processes that are at work today were at work in the past. Summarized by “THE PRESENT IS THE KEY TO THE PAST.” A gradual continuous change that accumulates with time for thousands and millions of years causing “significant change”. Uniformitarianism is a basic foundation of modern geology.
Age of the Earth
Estimated age for the Earth and the rest of the solar system is about 4.55 billion years. The oldest Earth rocks: 3.8 to 3.9 billion years Oldest Earth minerals (zircons): 4.2 billion years Oldest Moon rocks: 4.44 billion years
Early Earth Timeline
•About 5.5-6 billion years ago (BYA), the solar nebula begins to collapse •About 4.6 BYA, Sun begins fusion •About 4.5-4.56 BYA, Proto-Earth formed from planetesimals. •4.44+ BYA, Earth-Moon formed by giant impact. Earth melts, magma occurs. •4.2 BYA, Earth was completely differentiated. •4 BYA, earliest oceans formed, thick atmosphere exists •3.8 BYA, life develops •2.5-3 BYA, photosynthesis leads to O2 in ocean •2 BYA, O2 hits atmosphere
The Geologic Time Scale
Structure of the Time Scale
Based on their interpretations of the rock record, geologists have divided Earth’s 4.56-billion-year history into units that represent specific amounts of time. Taken together, these time spans make up the geologic time scale.
The Geologic Time Scale
Structure of the Time Scale
Eons represent the greatest expanses of time. Eons are divided into eras. Each era is subdivided into periods. Finally,
Lecturer Dr. Sameh Abu El Soud
History of Early Geology
Catastro‐phism Tries to explain the presence of everything on earth and their composition by catastrophes. E.g. A catastrophe happened to dinosaurs 80 million years ago. A comet fell on earth surface leading to volcanoes, leading to dust clouds in the atmosphere, preventing solar rays penetration , the plants died and then the dinosaurs.
Uniformi‐tarianism (James Hu on, late 1700s) ‐ He proposed that the same processes that are at work today were at work in the past. Summarized by “THE PRESENT IS THE KEY TO THE PAST.” A gradual continuous change that accumulates with time for thousands and millions of years causing “significant change”. Uniformitarianism is a basic foundation of modern geology.
Age of the Earth
Estimated age for the Earth and the rest of the solar system is about 4.55 billion years. The oldest Earth rocks: 3.8 to 3.9 billion years Oldest Earth minerals (zircons): 4.2 billion years Oldest Moon rocks: 4.44 billion years
Early Earth Timeline
•About 5.5-6 billion years ago (BYA), the solar nebula begins to collapse •About 4.6 BYA, Sun begins fusion •About 4.5-4.56 BYA, Proto-Earth formed from planetesimals. •4.44+ BYA, Earth-Moon formed by giant impact. Earth melts, magma occurs. •4.2 BYA, Earth was completely differentiated. •4 BYA, earliest oceans formed, thick atmosphere exists •3.8 BYA, life develops •2.5-3 BYA, photosynthesis leads to O2 in ocean •2 BYA, O2 hits atmosphere
The Geologic Time Scale
Structure of the Time Scale
Based on their interpretations of the rock record, geologists have divided Earth’s 4.56-billion-year history into units that represent specific amounts of time. Taken together, these time spans make up the geologic time scale.
The Geologic Time Scale
Structure of the Time Scale
Eons represent the greatest expanses of time. Eons are divided into eras. Each era is subdivided into periods. Finally,