Old Earth Ministries Online Geology Curriculum

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Geology - Chapter 1:  Introduction

    The study of the earth and its rocks is also a study of God's creation.  It is God who set the laws of nature which shape this planet's rocks into what they are today.  In order to get a full understanding of God's creation, we must study not only the lifeforms upon earth, and the stars in the sky...we must also study the rocks beneath our feet, and understand how they were formed.

     Geology (from Greek γη- (ge-, "the earth") and λογος (logos, "word", "reason")) is the scientific branch of study that examines the solid matter of a celestial body. Geologists, or those that study geology, examine the composition, structure, physical properties, and history of the planetary body. Most geologists study the earth. However, there are some that study planets, and they are known as planetary geologists.

Basic Composition

     The earth is made up of several layers.  The atmosphere of the earth is primarily studied by the branch of science known as climatology, or meteorology.   The layers of the earth's solid matter are studied by geologists.  Many geological features are caused by climatology, due to weathering of the rocks of the earth.

     The two main regions of the earth's surface are continents and ocean basins.  Continents are large landmasses, composed mostly of granite type rocks, but also composed of sedimentary and metamorphic rocks.  Ocean basins are the low-lying portion of the earth's surface which lies between the continental landmasses.

     The uppermost surface of the earth is called the crust.  There are two main types of crust.  Continental crust, which forms the exposed land masses of earth, is approximately 10 to 22 miles thick (16 to 35 kilometers).  The other type of crust is known as oceanic crust.  This type of crust is only 5 to 10 miles thick (8 to 16 kilometers).  The primary difference between these crusts is the mineral composition.  The density of oceanic crust causes it to sink in relation to continental crusts.  This is an important concept that will be discussed later when we consider tectonic forces.

      The shape and form of the earth's surface, including elevation differences, is known as topography.  Topography can be studied through the use of a topographic map (click the map for a larger view).  Each line on a topographic map represents a change of elevation.  The scale of each line can usually be found in the map legend.  Geologists receive training in order to make topographic maps.  For additional study on topographic maps, click here.

Continents

     There are several major features of continents.  Typically, continents have three parts.  The first part is known as a shield.  A shield is a regional area with low relief (little elevation change).  The elevation of a shield is typically within a few hundred yards of sea level.   For additional study of shields, click here.

     Another part of continents is the stable platform.  This feature is characterized by a covering of sedimentary rocks.  It is called stable because it has largely remained unchanged for many millions of years.  The stable platforms have never been subjected to uplifting tectonic forces.

     The third part of continents is known as folded mountain belts.  These mountains normally occur along the margins, although they can also form on the continents interior.  Typically, except for a few volcanoes, mountains form in belts, or ranges, because of the collision of two tectonic plates.  The image at right shows a picture of the Himalayan Mountains as seen from the International Space Station (click image for a larger view).  These mountain ranges can be thousands of miles long, and hundreds of miles wide.  Because of their formation from the collision of tectonic plates, they are great evidence that the earth's crust is in motion.

     It is important to note that although other planets have mountains, they do not have mountain ranges.  This is because they do not have tectonic plates which move about the surface of the earth.  For additional study, see mountain range.

Ocean Basins

     Despite what you might think, there is a lot of different topographic features underneath the world's oceans.  One of the most important features is the oceanic ridge.  The ridge is a broad, fractured uplift in the center of the oceans, and it can be as wide as 870 miles (1,400 kilometers).  At the center of this ridge is the rift valley, where new volcanic material is being expelled from the earth's mantle.  Because of the volcanic origin of the oceanic crust, it is mostly composed of a dense rock known as basalt.

     As the new material is expelled, the oceanic crust grows, and it is pushed away from the ridge by convection currents in the mantle.   This is known as seafloor spreading (see an short video on seafloor spreading (Not IPad compatible).  The further away from the ridge you go, the older the rocks of the oceanic crust are.   Most of the current oceanic crust is less than 150 million years old, whereas the age of the continental shields are typically around 700 million years old.  To learn more, see seafloor spreading.

     Another feature of the sea floor is called the abyssal floor.  This is the vast, broad areas that are relatively smooth, and they are typically about 6,500 to 9800 feet deep (2,000-3,000 meters).  The abyssal floor is further divided into to parts.  The abyssal hills are small hills rising several hundred meters above the surrounding ocean floor.  They are actually the most prevalent landform on earth, because the cover more than 80 percent of the Pacific Ocean floor.  Closer to the continents is an area known as the abyssal plains, which is composed mostly of eroded material from the continent.  For more learning, see abyssal plains.

     Seamounts are another prominent feature.  These are isolated peaks of volcanoes which are underwater.  Sometimes they can rise above sea level, such as the Hawaiian island chain.  Seamounts which rise above the surface are no longer called seamounts, and instead are referred to as islands.  To learn more, see seamount.

     One of the most fascinating features of the ocean floor are the trenches.  A trench is were the oceanic crust is diving beneath another section of crust.  The Mariana Trench is probably the most well known, as it is the deepest point in the world's oceans (and therefore the deepest point on the earth's crust).  It has a maximum depth of 35,798 feet, or 10,911 meters.  For more, see Mariana Trench.

     The final feature of the ocean floor that we will consider is the continental margins.  A continental margin is an area of transition between a continental mass and an ocean basin.  The submerged part of the continent is called a continental shelf.  Technically, it is part of the continent, even though it is underwater.  This is because it moves as a whole with the continental land mass.  For more, see continental shelf.

     The continental shelf can be up to 930 miles wide (1,500 kilometers), as is the case with the Siberian shelf.  The shelf itself slopes away from the continent.  This long slope is known as the continental slope.  This area is not perfectly flat.  It is cut in many places by underwater currents, or rivers, which form submarine canyons.  These can be quite large, and extend for hundreds of miles.  For more, see submarine canyons.

The Earth's Internal Structure

     The earth is made up of three main sections (click the picture for a higher resolution image).  The uppermost surface is called the crust.  The crust is also referred to as the lithosphere.  We have already discussed the crust of the earth.  Immediately below the crust is the mantle.  The mantle has two parts.  The upper part is known as the asthenosphere, or upper mantle.  It is approximately 125 miles thick (200 kilometers), and is partially molten.  It is from this portion that magma for some volcanoes originates.  For further reading, see Asthenosphere.  Below the asthenosphere is the solid mantle, which extends to a depth of about 1,800 miles (2,900 kilometers). 

     The center of the earth is known as the core.  It is divided into two portions, an inner core and an outer core.  The outer core is liquid, and extends to a depth of about 3,170 miles (5,100 kilometers).  The inner core is solid, with a radius of about 795 miles (1,278 kilometers).  The outer core's convection currents is thought to be the source of the earth's magnetic field. 

End of Chapter

Tuesday - Research

     Research the answers to the following questions.  Your parents may have you simply answer the questions, or they may have you put it in essay form.  Please follow your parents instructions.

Research the history and current occupations in geology.  To answer these questions, utilize a search engine to locate the best web pages, or consult a textbook/encyclopedia.  You may also use the links at the bottom of this page.

When did the science of geology first begin?

Who is called the "father of modern geology?"

Who were some of the early geologists?

What jobs do geologists do today?

How much money do geologists make?

Wednesday - Quiz

     Today you will complete an 11 question practice quiz.  The link to the quiz will open a new window.  You can come back here and check your answers.  Do not click the Back button during the quiz.  After the quiz, continue your research project, if necessary.

          Geology Chapter 1 Quiz

Thursday - Review

     Please review the terms in bold in the text, and ensure you have completed your research work from Tuesday.

Friday - Test

     Today you will take the end of chapter test.  Please close all other browser windows, and click on the link below.  During the test, do not click the Back button on your browser.

          Geology Chapter 1 Test

After you have completed the test, you may proceed to Chapter 2 on your next school day.  Please return to the introduction page for the link to the next chapter.

Return to the Old Earth Ministries Online Geology Curriculum homepage.

Helpful Links

History of Geology (Wikipedia)

History of Geology

What Geologists Do

The Study of Geology

Association for Women Geoscientists - Career Opportunities

Petroleum Geologists - Pay article

Geologist Pay at Salary.com

Mining Pay at Salary.com