Essentials of Geology 8e by rrboy

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									Essentials of Geology, 8e

Frederick K. Lutgens & Edward J. Tarbuck

An Introduction to Geology, Chapter 1

Essentials of Geology, 8e
Stan Hatfield and Ken Pinzke Southwestern Illinois College

The science of Geology
 Geology is the science that pursues an

understanding of planet Earth
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
 Physical

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

The science of Geology
 Some historical notes about geology
nature of Earth has been a focus of study for centuries  Catastrophism-a theory, now discredited,
that the geological features of the earth were formed by a series of sudden violent catastrophes rather than a gradual evolutionary process.
 The

The science of Geology
 Some historical notes about geology
nature of Earth has been a focus of study for centuries  Uniformitarianism-theory that the same
geologic processes occurred in the past as occur today, and that geologic formations and structures can be interpreted by observing present-day actions
 The

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

Geologic time
 The magnitude of geologic time
 Involves

vast times – millions or billions of

years  An appreciation for the magnitude of geologic time is important because many processes are very gradual

A view of Earth
 Earth is a planet that is small and self-

contained  Earth’s four spheres
of the earth’s surface that is water, including the seas and water in the atmosphere  Atmosphere-the mixture of gases that surrounds a celestial body such as the Earth
 Hydrosphere-the portion

A view of Earth
 Biosphere-the whole area

of the Earth’s surface, atmosphere, and sea that is inhabited by living things.

 Solid

Earth- all of the rocks and minerals

and underlying structures that compose the Earth

A view of Earth from the Moon

Earth as a system
 Earth is a dynamic planet with many

interacting parts or spheres  Parts of the Earth system are linked  Characterized by processes that
on spatial scales from fractions of millimeter to thousands of kilometers  Have time scales that range from milliseconds to billions of years
 Vary

Earth as a system
 The Earth system is powered by the Sun

that drives external processes in the
 Atmosphere  Hydrosphere

 At

Earth’s surface

Earth as a system
 The Earth system is also powered from

the Earth’s interior
 Heat

remaining from the formation and heat that is continuously generated by radioactive decay powers the internal processes that produce volcanoes, earthquakes, and mountains

The rock cycle: part of the Earth system
 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

Earth’s internal structure
 Earth’s internal layers can be defined by  Chemical composition  Physical properties

 Layers defined by composition  Crust - the thin outermost layer of the
Earth, approximately one percent of the Earth’s volume, that varies in thickness and has a different composition than the interior  Mantle - the part of the Earth or another planet that lies between the crust and core  Core - the central part of the Earth

Earth’s internal structure
 Four main layers of Earth are based on

physical properties and hence mechanical strength
 Lithosphere

- the solid outer layer of the

Earth above the asthenosphere, consisting of the crust and upper mantle  Asthenosphere - a weak zone in the upper part of the Earth’s mantle where rock can be deformed in response to stress, resulting in movement of the overlying crust

Earth’s internal structure
 Four main layers of Earth are based on

physical properties and hence mechanical strength
 Mesosphere  Core

– the lower portion of the

mantle that contacts the core

- innermost part of Earth; divided into

two parts, the outer core and the inner core.

Earth’s internal structure

Dynamic Earth
 The theory of plate tectonics

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

 Involves

Dynamic Earth
 The theory of plate tectonics
A

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 occurs along their boundaries

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

Dynamic Earth
 Plate boundaries  Transform 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

End of Chapter 1


								
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