Introduction to Geology. Chapter 1 Intro to Geology: summary in haiku form Here's geology. It's the study of the Earth - complete entity.

Transcription

1 Introduction to Geology Chapter 1 Intro to Geology: summary in haiku form Here's geology. It's the study of the Earth - complete entity. Geology - the science that pursues an understanding of planet Earth Physical geology examines the materials composing Earth and seeks to understand the many processes that operate beneath and upon its surface Historical geology seeks an understanding of the origin of Earth and its development through time Geology, people, and the environment Many important relationships exist between people and the natural environment Problems and issues addressed by geology include Natural hazards, resources, world population growth, and environmental issues Environmental Geology December 26, 2004 Sumatran Earthquake / Tsunami Environmental Geology La Conchita, 1995 People were warned, evacuated, none killed January 10, Not so lucky Environmental Geology January 31, 2006: Pakistan Earthquake Figure 1.3 Closer to home October 2007: (photos are one hour apart) Some historical notes about geology The nature of Earth has been a focus of study for centuries Catastrophism Uniformitarianism and the birth of modern geology History of Geology Catastrophism landscapes have been influenced by great catastrophes Popular during 18 th and 19 th centuries Uniformitarianism present is the key to the past Advanced by Hutton ( Father of Geology ) in the late 1700 s, and Lyell in the 1800 s Catastrophism? Velikovsky (1950 s) Venus a comet ejected from Jupiter 1

2 W. & L. Alvarez (1980) asteroid struck Earth 65 Ma, caused dinosaur extinction Super Volcanoes, such as Yellowstone, Toba, etc The debate continues Geologic time The magnitude of geologic time Involves vast expanses of time millions or billions of years An appreciation for the magnitude of geologic time is important because many processes are very gradual Geologic time Geologists are now able to assign fairly accurate dates to events in Earth history and the geologic time scale means that dates are placed in their proper sequence or order without knowing their age in years Knightia, from Wyoming fossil fern The Geologic Time Scale Grand Canyon from South Kaibab Trail The Scientific Method The nature of scientific inquiry How or why things happen is explained using a(n): Hypothesis a tentative (or untested) explanation Theory a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts The nature of scientific inquiry Scientific method involves Gathering facts through observations Formulation of hypotheses and theories There is no fixed path that scientists follow that leads to scientific knowledge Field Studies Field Studies Remote Sensing Remote Sensing The Scientific Method Actual Scientific Method (joke!) Earth s Spheres: Hydrosphere dynamic mass of water ocean blankets 71% of surface to average depth of 3800 meters (97% of earth s water) Atmosphere life-giving gaseous envelope half below an altitude of 5.6 km, 90% less than 16 km Biosphere all life on Earth concentrated near the surface Geosphere bulk of mass of the Earth 2

3 radius of 6400 km Magnetosphere magnetic field Cryosphere ice Earth as a System: System Group of interacting, or interdependent, parts that form a complex whole Earth is a dynamic planet with many interacting parts or spheres Earth System Science Aims to study composed of numerous interacting parts or subsystems Employs an interdisciplinary approach to solve global environmental problems What is a system? Any size group of interacting parts that form a complex whole Open vs. closed systems Feedback mechanisms Negative feedback maintains the status quo Positive feedback enhances or drives changes The Earth system is powered by the Sun that drives external processes in the: Atmosphere Hydrosphere At Earth s surface The Earth system is also powered by Earth s interior Sources of Energy: Heat from the earth s interior Powers the internal processes that produce volcanoes, earthquakes, and mountains Basic rock types Igneous rocks Cooling and solidification of magma (molten rock) Examples include granite (intrusive) and basalt (extrusive) Vulcan s Throne, Grand Canyon granite boulders in ABDSP lichens on granite Basic rock types (continued) Sedimentary rocks Accumulate in layers at Earth s surface Sediments are derived from weathering of preexisting rocks Examples include sandstone & limestone 12 seconds at the rim (not!) 3

4 Basic rock types (continued) Metamorphic rocks Formed by changing preexisting igneous, sedimentary or other metamorphic rocks Driving forces are increased heat and pressure Examples include gneiss and marble A nice metamorphic rock The Rock Cycle: One of Earth s subsystems The loop that involves the processes by which one rock changes to another Illustrates the various processes and paths as earth materials change both on the surface and inside the Earth The Rock Cycle: Interactions: Nebular Hypothesis Describes the birth of the Solar System Enormous rotating cloud: solar nebula Nebular Hypothesis of Solar System Formation Nebular Hypothesis Inner planets high temp s, weak gravitational fields, unable to grab lighter elements Outer planets colder, huge amounts of lighter elements Early evolution of Earth Formation of Earth s layered structure Metals sank to the center Molten rock rose to produce a primitive crust Chemical segregation established the three basic divisions of Earth s interior Primitive atmosphere evolved from gases in Earth s interior Earth s internal structure Layers defined by composition Crust Mantle Core Layers defined by physical properties Lithosphere Asthenosphere Mesosphere Inner and Outer Core Internal Structure of Earth Divided into layers based on: 1. Composition 2. Physical properties Continents and Ocean Basins The Pacific Ocean Basin Atlantic & Indian Ocean Basins Shields & Mountains 4

5 Continental Features Medicine Bow Mountains, Wyoming Edge of the Canadian Shield (North Dakota) The face of Earth Ocean basins Continental margins Includes the continental shelf, continental slope, and the continental rise Deep-ocean basins Abyssal plains Oceanic trenches Seamounts The face of Earth Ocean basins Oceanic ridge system Most prominent topographic feature on Earth Composed of igneous rock that has been fractured and uplifted End of Introduction to Geology 5