Changes

About two thirds of the Earth's surface lies beneath the oceans. Before the 19th century, the depths of the open ocean were largely a matter of speculation, and most people thought that the ocean floor was relatively flat and featureless. However, as early as the 16th century, a few intrepid navigators, by taking soundings with hand lines, found that the open ocean can differ considerably in depth, showing that the ocean floor was not as flat as generally believed. Oceanic exploration during the next centuries dramatically improved our knowledge of the ocean floor. We now know that most of the geologic processes occurring on land are linked, directly or indirectly, to the dynamics of the ocean floor.

About two thirds of the Earth's surface lies beneath the oceans. Before the 19th century, the depths of the open ocean were largely a matter of speculation, and most people thought that the ocean floor was relatively flat and featureless. However, as early as the 16th century, a few intrepid navigators, by taking soundings with hand lines, found that the open ocean can differ considerably in depth, showing that the ocean floor was not as flat as generally believed. Oceanic exploration during the next centuries dramatically improved our knowledge of the ocean floor. We now know that most of the geologic processes occurring on land are linked, directly or indirectly, to the dynamics of the ocean floor.

"Modern" measurements of ocean depths greatly increased in the 19th century, when deep-sea line soundings (bathymetric surveys) were routinely made in the Atlantic and Caribbean. In 1855, a bathymetric chart published by U.S. Navy Lieutenant Matthew Maury revealed the first evidence of underwater mountains in the central Atlantic (which he called "Middle Ground"). This was later confirmed by survey ships laying the trans-Atlantic telegraph cable. Our picture of the ocean floor greatly sharpened after World War I (1914-18), when echo-sounding devices -- primitive sonar systems -- began to measure ocean depth by recording the time it took for a sound signal (commonly an electrically generated "ping") from the ship to bounce off the ocean floor and return. Time graphs of the returned signals revealed that the ocean floor was much more rugged than previously thought. Such echo-sounding measurements clearly demonstrated the continuity and roughness of the submarine mountain chain in the central Atlantic (later called the Mid-Atlantic Ridge) suggested by the earlier bathymetric measurements.

"Modern" measurements of ocean depths greatly increased in the 19th century, when deep-sea line soundings (bathymetric surveys) were routinely made in the Atlantic and Caribbean. In 1855, a bathymetric chart published by U.S. Navy Lieutenant Matthew Maury revealed the first evidence of underwater mountains in the central Atlantic (which he called "Middle Ground"). This was later confirmed by survey ships laying the trans-Atlantic telegraph cable. Our picture of the ocean floor greatly sharpened after World War I (1914–18), when echo-sounding devices—primitive sonar systems—began to measure ocean depth by recording the time it took for a sound signal (commonly an electrically generated "ping") from the ship to bounce off the ocean floor and return. Time graphs of the returned signals revealed that the ocean floor was much more rugged than previously thought. Such echo-sounding measurements clearly demonstrated the continuity and roughness of the submarine mountain chain in the central Atlantic (later called the Mid-Atlantic Ridge) suggested by the earlier bathymetric measurements.

In 1947, seismologists on the U.S. research ship Atlantis found that the sediment layer on the floor of the Atlantic was much thinner than originally thought. Most scientists had previously believed that the oceans have existed for at least four billion years, so therefore the sediment layer should have been very thick. Why then was there so little accumulation of sedimentary rock and debris on the ocean floor? Their answer to this question, which came after further exploration, would prove to be vital to advancing the concept of plate tectonics.

In 1947, seismologists on the U.S. research ship Atlantis found that the sediment layer on the floor of the Atlantic was much thinner than originally thought. Most scientists had previously believed that the oceans have existed for at least four billion years, so therefore the sediment layer should have been very thick. Why then was there so little accumulation of sedimentary rock and debris on the ocean floor? Their answer to this question, which came after further exploration, would prove to be vital to advancing the concept of plate tectonics.

In the 1950s, oceanic exploration greatly expanded. Data gathered by oceanographic surveys conducted by many nations led to the discovery that a great mountain range on the ocean floor virtually encircled the Earth. Called the global mid-ocean ridge, this immense submarine mountain chain -- more than 50,000 kilometers (km) long and, in places, more than 800 km across -- zig-zags between the continents, winding its way around the globe like the seam on a baseball. Rising an average of about 4,500 meters(m) above the sea floor, the mid-ocean ridge overshadows all the mountains in the United States except for  [[Denali]] (formerly known as [[Mount McKinley]]) in Alaska (6,194 m). Though hidden beneath the ocean surface, the global mid-ocean ridge system is the most prominent topographic feature on the surface of our planet.

In the 1950s, oceanic exploration greatly expanded. Data gathered by oceanographic surveys conducted by many nations led to the discovery that a great mountain range on the ocean floor virtually encircled the Earth. Called the global mid-ocean ridge, this immense submarine mountain chain—more than 50,000 kilometers (km) long and, in places, more than 800 km across—zig-zags between the continents, winding its way around the globe like the seam on a baseball. Rising an average of about 4,500 meters(m) above the sea floor, the mid-ocean ridge overshadows all the mountains in the United States except for  [[Denali]] (formerly known as [[Mount McKinley]]) in Alaska (6,194 m). Though hidden beneath the ocean surface, the global mid-ocean ridge system is the most prominent topographic feature on the surface of our planet.

== Magnetic Striping and Reversals ==

== Magnetic Striping and Reversals ==

Beginning in the 1950s, scientists, using [[magnetism|magnetic]] instruments (magnetometers) adapted from airborne devices developed during [[World War II]] to detect [[submarine]]s, began recognizing odd magnetic variations across the ocean floor, showing reversals in the Earth's magnetic field over it's history. This finding, though unexpected, was not entirely surprising because it was known that basalt -- the iron-rich, volcanic rock making up the ocean floor-- contains a strongly magnetic mineral (magnetite) and can locally distort compass readings. This distortion was recognized by Icelandic mariners as early as the late 18th century. More important, because the presence of magnetite gives the basalt measurable magnetic properties, these newly discovered magnetic variations provided another means to study the deep ocean floor.

Beginning in the 1950s, scientists, using [[magnetism|magnetic]] instruments (magnetometers) adapted from airborne devices developed during [[World War II]] to detect [[submarine]]s, began recognizing odd magnetic variations across the ocean floor, showing reversals in the Earth's magnetic field over it's history. This finding, though unexpected, was not entirely surprising because it was known that basalt—the iron-rich, volcanic rock making up the ocean floor—contains a strongly magnetic mineral (magnetite) and can locally distort compass readings. This distortion was recognized by Icelandic mariners as early as the late 18th century. More important, because the presence of magnetite gives the basalt measurable magnetic properties, these newly discovered magnetic variations provided another means to study the deep ocean floor.

== Explanations of continental drift ==

== Explanations of continental drift ==

The breaking up of one land mass into the separate continents was first proposed by the [[France|French]] [[creation scientist]] [[Antonio Snider]] in 1859,<ref name="Snider">Batten, Don, et. al., The Creation Answers Book, chapter 11: [http://creationontheweb.com/images/pdfs/cabook/chapter11.pdf What about continental drift?], p. 157, 2007</ref> who astutely observed an almost perfect match between the coastlines of western [[Africa]] and eastern [[South America]], which suggested they had once been joined. The idea was later taken up by [[Alfred Wegener]] in the 1930s."<ref name=wcd> [http://www.scientus.org/Wegener-Continental-Drift.html Wegener and Continental Drift Theory]</ref> [[Atheists]] mocked the concept for about 100 years (see [[scientific bias]]), until finally accepting its truth in the 1960s.<ref name="Snider" />  

The breaking up of one land mass into the separate continents was first proposed by the [[France|French]] [[creation scientist]] [[Antonio Snider]] in 1859,<ref name="Snider">Batten, Don, et. al., The Creation Answers Book, chapter 11: [http://creationontheweb.com/images/pdfs/cabook/chapter11.pdf What about continental drift?], p. 157, 2007</ref> who astutely observed an almost perfect match between the coastlines of western [[Africa]] and eastern [[South America]], which suggested they had once been joined. The idea was later taken up by [[Alfred Wegener]] in the 1930s."<ref name=wcd>[http://www.scientus.org/Wegener-Continental-Drift.html Wegener and Continental Drift Theory]</ref> [[Atheists]] mocked the concept for about 100 years (see [[scientific bias]]), until finally accepting its truth in the 1960s.<ref name="Snider" />  

Although Snider and Wegener did not have an explanation of the cause of continental drift, the rigid discipline of [[creation science]] allied with [[Faith and science|faith and logic]] eventually enabled creation scientist to interpret [[Biblical scientific foreknowledge]] in order to explain how a relatively recent cataclysmic event caused the separation of the still-moving continents from one land mass. Genesis 1:9-10 describes how all of dry land was in one place.<ref>http://www.christiananswers.net/q-aig/aig-c001.html#1</ref>  The continental drift occurring during the [[Great Flood]] when the earth was divided (Genesis 10:25).

Although Snider and Wegener did not have an explanation of the cause of continental drift, the rigid discipline of [[creation science]] allied with [[Faith and science|faith and logic]] eventually enabled creation scientist to interpret [[Biblical scientific foreknowledge]] in order to explain how a relatively recent cataclysmic event caused the separation of the still-moving continents from one land mass. Genesis 1:9-10 describes how all of dry land was in one place.<ref>http://www.christiananswers.net/q-aig/aig-c001.html#1</ref>  The continental drift occurring during the [[Great Flood]] when the earth was divided (Genesis 10:25).

==References==

==References==

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[[category:geology]]

[[Category:Geology]]