Midterm 1 Review
Based on the textbook: Understanding Earth, 6th Edition, by Grotzinger and Press CH 1: earth system
The human creative process, field and lab observations, and experiments help geoscientists formulate testable hypotheses (models) for how the Earth works and its history. A hypothesis is a tentative explanation focusing attention on plausible features and relationships of a working model. If a testable hypothesis is confirmed by a large body of data, it may be elevated to a theory. Theories are abandoned when subsequent investigations show them to be false. Confidence grows in those theories that withstand repeated tests and successfully predict the results of new experiments. A set of hypothesis and theories may become the basis of a scientific model that represents an entire system too complicated to replicate in the laboratory. Often models are tested and revised in a series of computer simulations. Confidence in such a model grows as it successfully predicts the behavior of the system. The elevations of Earth topography averages 1–2 kilometers above sea level for land features and 4–5 kilometers below sea level for features of the deep ocean. The principle of uniformitarianism states that geological processes have worked in the same way throughout time.
Earth’s interior is divided into concentric layers (crust, mantle, core) of sharply different chemical composition and density. The layered composition of the Earth is driven by gravity. Only eight of the 100 or so elements account for 99 percent of Earth’s mass. The lightest element (oxygen) is most abundant in the surface crust and mantle, while the densest (iron) makes up most of what is found deep in the core. Earth’s major interacting systems are the climate system, the plate tectonic system, and the geodynamic system. The climate system involves interactions among the atmosphere, hydrosphere, and biosphere. The plate tectonic system involves interactions among the lithosphere, asthenosphere, and deep mantle. The geodynamic system involves interactions within the central core that produce occasional reversals of Earth’s magnetic field.
As the Earth cooled, an outer relatively rigid shell, called the lithosphere, formed. Dynamic processes driven by heat transfer, density differences, and gravity broke the outer shell into plates that move around the Earth at rates of centimeters per year. Major components (atmosphere, hydrosphere, biosphere) of Earth’s surface systems are driven mostly by solar energy. Earth’s internal heat energizes the lithosphere, asthenosphere, deep mantle, and outer and inner core.
Terms and Concepts
Plate tectonic system
Principle of uniformitarianism
CH 2: plate tectonics
For over the last century some geologists have argued for the concept of continental drift based on:
the jigsaw-puzzle fit of the coasts on both sides of the Atlantic the geological similarities in rock ages and trends in geologic structures on opposite sides of the Atlantic
fossil evidence suggesting that continents were joined at one time the distribution of glacial deposits as well as other paleoclimatic evidence
In the last half of the twentieth century the major elements of the plate tectonic theory were formulated. Starting in the 1940s (WWII), ocean floor mapping began to reveal major geologic features on the ocean floor. Then, the match between magnetic anomaly patterns on the seafloor with the paleomagnetic time scale revealed that the ocean floor had a young geologic age and was systematically older away from the oceanic ridge systems. The concepts for seafloor spreading, subduction, and transform faulting evolved out of these and other observations.
According to the theory of plate...