Copyright (c) 2005 Pearson Education Canada, Inc.1-1 PowerPoint Presentation Stan Hatfield. Southwestern Illinois College Ken Pinzke. Southwestern Illinois College Charles Henderson. University of Calgary Chapter 1 An Introduction to Geology

Copyright (c) 2005 Pearson Education Canada Inc.1-2 The Science of Geology Geology is 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

Copyright (c) 2005 Pearson Education Canada Inc.1-3 The Science of Geology Geology, people, and the environment There are many important relationships between people and the natural environment Some of the problems and issues addressed by geology involve natural hazards, resources, world population growth, and environmental issues

Copyright (c) 2005 Pearson Education Canada Inc.1-4 The Science of Geology A Canadian Profile Sir William Edmond Logan has been called Canada’s #1 scientist in history He was the first director of the GSC and was active in the outdoor pursuits of geology

Copyright (c) 2005 Pearson Education Canada Inc.1-5 The Science of Geology Some historical notes about geology The nature of Earth has been a focus of study for centuries Catastrophism: shaping of the Earth’s landscape by catastrophes Uniformitarianism: a principle first proposed by James Hutton that represented the Birth of Modern Geology (processes that operated in the past also operate today)

Copyright (c) 2005 Pearson Education Canada Inc.1-6 Geologic Time Geologists are now able to assign fairly accurate dates to events in Earth history Relative dating and the Geologic Time Scale Relative dating means that dates are placed in their proper sequence or order without knowing their age in years (apply Principles of Superposition and Fossil Succession)

Copyright (c) 2005 Pearson Education Canada Inc.1-7 Geologic Time The magnitude of geologic time Involves vast times – millions or billions of years (the Earth is 4.5 Billion years old!) An appreciation for the magnitude of geologic time is important because many processes are very gradual

Copyright (c) 2005 Pearson Education Canada Inc.1-8 Geologic Time The Geologic Time Scale. The numbers are absolute ages in millions of years before present. Note that the Precambrian accounts for 88% of geologic time and yet the Phanerozoic with its wealth of fossils includes many divisions (Eras, Periods, Epochs).

Copyright (c) 2005 Pearson Education Canada Inc.1-9 The Nature of Scientific Inquiry Science assumes the natural world is consistent and predictable Goal of science is to discover patterns in nature and use the knowledge to make predictions Scientists collect “facts” through observation and measurements

Copyright (c) 2005 Pearson Education Canada Inc.1-10 The Nature of Scientific Inquiry How or why things happen is explained using a Hypothesis – a tentative (or untested) explanation Theory – a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts

Copyright (c) 2005 Pearson Education Canada Inc.1-11 The Nature of Scientific Inquiry Scientific Methods Scientific method involves gathering facts through observations and creative formulation of hypotheses and theories There is no fixed path that scientists follow that leads to scientific knowledge

Copyright (c) 2005 Pearson Education Canada Inc.1-12 A View of Earth Earth is a planet that is small and self- contained Earth’s four spheres Hydrosphere Atmosphere Biosphere Solid Earth

Copyright (c) 2005 Pearson Education Canada Inc.1-13 A View of Earth The breathtaking beauty of Earth as seen by the Apollo astronauts in the 1960s and 1970s.

Copyright (c) 2005 Pearson Education Canada Inc.1-14 Earth as a System Earth is a dynamic planet with many interactions among the four spheres Hydrosphere Atmosphere Biosphere Solid Earth

Copyright (c) 2005 Pearson Education Canada Inc.1-15 Earth as a System Parts of the Earth system are linked Characterized by processes that Vary on spatial scales from fractions of a millimetre to thousands of kilometres Have time scales that range from milliseconds to billions of years

Copyright (c) 2005 Pearson Education Canada Inc.1-16 Earth as a System The Earth system is powered by the Sun that drives external processes in the Atmosphere Hydrosphere Earth’s Surface

Copyright (c) 2005 Pearson Education Canada Inc.1-17 Earth as a System The Earth system is also powered by the Earth’s interior Heat remaining from the formation and heat that is continuously generated by radioactive decay power the internal processes that produce volcanoes, earthquakes, and mountains

Copyright (c) 2005 Pearson Education Canada Inc.1-18 The rock cycle: part of the Earth System The loop that involves the processes by which one rock type changes to another Illustrates the various processes and paths as earth materials change both on the surface and inside the Earth

Copyright (c) 2005 Pearson Education Canada Inc.1-19 The rock cycle: part of the Earth System Rocks constantly form, change, and reform over longs spans of time.

Copyright (c) 2005 Pearson Education Canada Inc.1-20 The Face of Earth Earth’s surface has two principal divisions Continents Ocean Basins Significant difference between the continents and ocean basins is their relative levels

Copyright (c) 2005 Pearson Education Canada Inc.1-21 The Face of Earth Continents Most prominent features are linear mountain belts Shields Ocean Basins Ocean ridge system – the most prominent topographic feature on Earth Deep-ocean trenches

Copyright (c) 2005 Pearson Education Canada Inc.1-22 Early Evolution of Earth Origin of Planet Earth Most researchers believe that Earth and the other planets formed at essentially the same time from the same primordial material as the Sun Nebular hypothesis Layered structure developed by chemical segregation early in the formation of Earth

Copyright (c) 2005 Pearson Education Canada Inc.1-23 Earth’s Internal Structure Earth’s internal layers can be defined by Chemical composition Physical properties Layers defined by composition Crust Mantle Core

Copyright (c) 2005 Pearson Education Canada Inc.1-24 Earth’s Internal Structure Four main layers of Earth are based on physical properties and hence mechanical strength Lithosphere Asthenosphere Mesosphere (or Lower Mantle) Inner and Outer Core

Copyright (c) 2005 Pearson Education Canada Inc.1-25 Earth’s Internal Structure Views of the Earth’s layered structure.

Copyright (c) 2005 Pearson Education Canada Inc.1-26 Dynamic Earth The Theory of Plate Tectonics Involves understanding the workings of our dynamic planet Began in the early part of the twentieth century with a proposal called continental drift – the idea that continents moved about the face of the planet

Copyright (c) 2005 Pearson Education Canada Inc.1-27 Dynamic Earth The Theory of Plate Tectonics Theory called plate tectonics has now emerged that provides geologists with the first comprehensive model of Earth’s internal workings Plate Boundaries All major interactions among individual plates occur along their boundaries

Copyright (c) 2005 Pearson Education Canada Inc.1-28 Dynamic Earth Plate Boundaries Divergent boundary – two plates move apart, resulting in upwelling of material from the mantle to create new seafloor Convergent boundary – two plates move together with subduction of oceanic plates or collision of two continental plates

Copyright (c) 2005 Pearson Education Canada Inc.1-29 Dynamic Earth Mosaic of rigid plates and divergent and convergent boundaries.

Copyright (c) 2005 Pearson Education Canada Inc.1-30 Dynamic Earth Plate Boundaries Transform fault boundaries - located where plates grind past each other without either generating new lithosphere or consuming old lithosphere Changing boundaries - new plate boundaries are created in response to changes in the forces acting on the lithosphere

Copyright (c) 2005 Pearson Education Canada Inc.1-31 Dynamic Earth Mosaic of rigid plates and a transform fault boundary.

Copyright (c) 2005 Pearson Education Canada Inc.1-32 End of Chapter 1