INTRODUCTION

· The purpose of the introduction is to show the variety of topics covered in this course, treat in detail specific concepts which are common to many topics, and show their relevance

· Hopefully, the introduction will stimulate your interest for this course

Introduction

A. Definition of geology and the scientific method(see pages 8 & 9 for scientific method)

Geology is the science that examines the Earth, its form and composition and the changes that it has undergone and is undergoing
In the Scientific Method, a proposed idea needs to have adequate supportive data to be accepted fact. An example is the data that was necessary to support the Continental Drift theory or idea—jig saw puzzle alignment of continents; same rocks, fossils and glaciated areas on pre-joined continental mass (proto-continent).—see pages 363- 366 in text for pictures of data

B. Time and geology

time is a very important factor in the formation of geologic features--geologic processes usually act so slow that changes may not be visible during a lifetime--the two photos below were taken from the same vantage point nearly 100 years apart.
click here to see photos

1.Relative time

· geologic events can be observed as happening in a sequential order and not a certain number of years ago

· in a sequence of 3 events, one happened first, another second and the other last

2. Absolute time

· refers to the number of years ago the geologic event(s) happened (usually the event(s) happened millions or billions of years ago)

· "elephant rocks" in SE Missouri formed over a billion years ago while the limestone rocks in the Springfield area formed about 350 million years ago

· radioactivity in rocks allows us to determine how old a geologic event is-we will study this in detail later

· the application of relative and absolute time concepts to geologic events was important in developing the geologic time scale

3. Geologic time scale--- see page 7 in text

· consists of time divisions called eons, eras, periods and epochs

· eons are the longest in time duration, and epochs, the shortest

· specific happenings are associated with each division

· a division ends or begins based primarily on the changes in life forms on earth and times involving non-deposition or long term erosion of rock materials--the most important change in life forms found in the rocks as fossils would warrant a change from one eon to another and a lesser, but still important change, would warrant a change of one era to another and so forth down to the change of one epoch to another

· the extinction of dinosaurs established the ending of the Mesozoic era and beginning of the Cenozoic era--that boundary in time took place about 66.4 million years ago according to the geologic time scale

· many extinctions of life forms throughout geologic time may be caused by meteor impact with Earth

· some small geologic features in a linear pattern over Missouri and may represent meteor impact—Weableau structure.

· click here to see the geologic time scale-the numbers on the chart refer to millions of years ago

C. Uniformitarianism

is an important postulate in geology which states: "the same process(es) operating in the present to cause a geologic feature(s) operated in same way in the past to cause a similar feature"
the laws of nature are unchanging and the present is a key to the past

D. Earth materials (minerals and rocks)

1. Minerals

· naturally occurring individual chemical substances

· many have important uses--some examples are:

o minerals as gemstones---sapphires, rubies, emeralds, amethyst

o minerals as important sources of chemical elements---barium, iron, lead

o minerals as precious metals---gold, platinum, silver

· minerals comprise the composition of rock families

2. Rock families

· igneous rocks

o formed from the cooling of molten material (magma) at or near Earth’s surface (extrusive) or deep below (intrusive)

o geothermal energy is available to us as the result of igneous rock activity

· sedimentary rocks

o formed primarily in large bodies of water by physical, biological or chemical processes at low temperatures

o formed in layers and contain fossils which lend important information on history of life on Earth--the layering nature of sedimentary rocks is one of the most common characteristic of this family of rock

o click here to see stratified (layered) sedimentary rocks

· metamorphic rocks

o formed from any pre-existing rock which is subjected to high temperature and/or high pressure conditions for long time intervals with little or no melting of rocks in the metamorphic process

3. Rock cycle---see page 19 in text

· shows the inter-relationship between the 3 rock families---how a rock family forms and the conditions which help bring about the change of rocks in one family to another

· click here to see another the rock cycle

E. Volcanic activity

gasses and/or molten rocks emitted at surface of Earth
click here to see a volcanic eruption
eruption can be passive (gentle) or explosive (violent)
The "ring of fire" circumscribing the Pacific Ocean basin is the largest concentration of volcanic activity on Earth
there are benefits generated from volcanic or igneous activity such as fertile soils and geothermal energy in some places on Earth

F. Earth's interior, continental drift, and rock plates

1. Internal structure of Earth---see page 23 in text

· comprised of a crust, mantle, outer and inner core

· click here to see the structure of the Earth

· a. crust

o comprised primarily of a layer of granite (continental crust) and basalt layer (ocean crust) with some sediments on top

· b. mantle

o comprised of 3 sections, top and bottom portions are solid and center section (asthenosphere) is hot and viscous and may be considered part of the "upper mantle"

o c. core comprised of a top or outer liquid layer and a solid lower or inner portion-- both sections are comprised primarily of iron (Fe) and nickel (Ni)

· d. lithosphere

o entire rigid outer portion of Earth above asthenosphere including upper solid mantle and all the crust

o this section also includes any rock formed on top of the upper crust much later in formation than the upper crust

o    isostacy is a floating balance between the lithosphere and asthenosphere---this principle can explain why there is adjustment to this and some mountainous or elevated areas as well as certain low areas on Earth. Isostacy can be caused by some of the following:
        a. lithosphere floats on asthenosphere like balsa wood on water, denser materials sink, less dense, float—thicker but same
           density materials float higher---mountain belts have thicker roots—also, erosion of rock materials or melting glacial ice
           causes adjustment by the rebounding of rock below like the rebound of a filled balloon after pressure is released –see bottom of page 9 in text to show floating balance— pages 432 and 433 to show how isostacy affects mountain belts. This can also happen with glaciation

o            b. higher heat concentration in the lithosphere causing that portion
             of the lithosphere to rise because it is less dense than the
             surrounding rock of the same composition (heat or heated materials
             rise). The less dense rock rises and breaks into cracks called faults or
             fractures.

click here to see the detailed upper structure of Earth

2. Continental drift

· a single super "proto-continent" split into sections and drifted apart beginning about 150- 200 million years ago

· much data supports this idea including the map fit (jig saw puzzle) of continents

· click here to see the "map fit"

3. Rock plate concept (plate tectonics)---see page 30-31 in text

· born from the continental drift concept and explains the lithosphere as a series of plates each bounded to another or others

· plates can move towards boundaries (convergent), away from boundaries (divergent), or along boundaries (transformed)

· convergent boundaries form trenches where rocks plunge into the asthenosphere and divergent boundaries form ridges or rifts
where new rocks are formed

· the driving force of plate movement are convection cells

· click here to see world plates and boundaries

· plate boundaries are related to important geologic phenomena as volcanoes and earthquakes

G. Geologic structures

deep seated folded rocks on a large scale can harbor important deposits such as oil, gas and faulted rocks can contain precious metals
long term non-deposition or erosion of rocks can form unconformities which can aid in dividing geologic time
click here to see more about unconformities

H. Weathering and erosion

weathering is the breaking down of a rock or mineral material
weathering can be chemical or physical
click here to see the chemical weathering of a stone monument--note the pitting
stream water, wind and glacial ice are important transportation agents
an important product of weathering and erosion is soil--weathering and erosion acting together can form some spectacular landforms as Bryce Canyon in Utah
click here to see Bryce Canyon

I. Surface streams and groundwater

these are 2 very important sources of municipal water
there are pollution problems associated with these which we will consider later in the semester---pollution sources as landfills, factories, septic tanks, etc.
also important erosional and depositional features associated with these will be treated in detail such as caves and stalactites
click here to see cave deposits
important features as sinkholes formed from the action of groundwater can cause structural failure of buildings and considerable surface collapse
click here to see a large sinkhole

J. Glaciers

some depositional features caused by glaciers are important in the cement and concrete industries
during the "Great Ice Age" of North America glaciers cut the basin of the Great Lakes and was the source of much of the lake water
click here to see the extent of global ice cover during "Great Ice Age"
the glacial ice of Greenland and Antarctica comprises about 96% of all global ice and if all of the ice melted sea level would rise about 215 feet which means any coastal land presently below 215 feet elevation would be submerged

K. Earthquakes

seismology is the study of earthquakes
the New Madrid Fault area in southeast Missouri produced one of the largest earthquakes in history in the early 19th century--a possibility of large earthquakes happening in the future in this area is high
tsunami is a sea wave produced by an earthquake--these features have produced major damage in the past
click here for tsunami information