Earth’s Historical Archives: Rocks, Strata, and Geological Principles

Posted on Mar 31, 2025 in Geology

Earth’s Historical Archives: Rocks and Geological Processes

Rocks, historical archives of the Earth, are formed in geological processes and are recorded, useful for:

Conserving traces of the environment: where sediments were deposited, undergoing transformations by high temperatures and pressures.
Containing fossils: they provide information on what inspired it, can know the age of rocks and environmental conditions in which it was.
The information is recorded in strata in chronological order and serves to reconstruct the history of the Earth, using stratigraphy, dating, and geological principles.

Stratum: each of the layers in the sedimentary rocks that are, when the wall and the roof.

Stratigraphic sequence: two or more layers.
Stratigraphic series: two or more separate sequences.
Discontinuities: interrupt stratigraphic calls.
Discordance erosion: during the interruption of the deposit, the oldest series deformed and eroded, after she puts on her modern strata.

Dating: ordination of events in a geological time scale.

Absolute dating: measuring exact time, biological methods (related to time intervals, trees), sedimentological (deposits of sediments, glacial varves) and radioactive elements (uranium or carbon-14 content in rocks).

Basic geological principles serve to interpret the sediment record in almost all stratigraphic series:

Principle of Original Horizontality: Sediments accumulate in horizontal layers.
Principle of Lateral Continuity: A stratum has the same age throughout its extension, representing a brief episode in Earth’s history.
Principle of Superposition: The oldest layers are located at the base, with the most modern layers above.
Principle of Uniformitarianism: The current geological processes are the same as in the past; the laws that govern them have been constant in a slow, uniform, and gradual manner.
Principle of Faunal Succession: Strata deposited in different time periods contain different fossils, and strata containing the same fossils are of the same age.

Era: 4030 million years ago (85% of Earth’s history).
Geographical features: various continental masses are grouped into Pangea 1, with time breaks.
Forces of nature: fusion of the planet, magmatic and metamorphic processes originate terrestrial and continental crust.
Weather: inhospitable and different from the present, low temperature causes condensation of vapor and precipitation increases, giving rise to the hydrosphere.
Life: 3800 million years ago, life arises (ancient fossil-like current pseudofossils); seudofosiles appear (photosynthetic organisms that enrich oxygen and cause extinction 1), in the end life is diversified into 5 kingdoms (remains of trace fossils).

Era: 340 million years ago.
Features: several continents separated by oceans, with Pangea 2 are grouped.
Phenomena: Caledonian Orogeny ridges originated, very eroded relief.
Weather: geographical change by scaling up, 2 large glacial (warm and wet periods), with Pangea 2 extreme weather.
Life: abundant invertebrates, plants colonize the land makes 400 million years ago appear first vertebrates like fish, resulting in amphibians and reptiles, plants: 1 similar to algae, fern forests are important carbon deposits exploited now, with the plants increased insect.
Other: history very well reconstructed, comprehensive record.

Era: 165 million years ago (age of reptiles).
Features: Pangea 2 fragments into several continents and new oceans (Atlantic and Indian).
Phenomena: marine sediments are deposited, with mountain ranges of Alpine Orogeny (Late Cretaceous-Cenozoic).
Life: at sea mollusks, land plants are forests, colonizing the land reptiles (dinosaurs, pterosaurs that could fly), the birds come from dinosaurs, reptiles evolve into mammals, at the end of gretacico occurs 5th extinction by asteroid.