Compressed Zip File
Be sure that you have an application to open this file type before downloading and/or purchasing.
History Channel's How the Earth Was Made is a wonderful earth science documentary series. The episode titled "Loch Ness" is the story of the dark Scottish loch known for its fabled monster. Modern investigation reveals the loch to be the product of plate tectonics, faulting, and glacial activity. The episode is set up as a type of detective story, with evidence shown to back up a hypothesis. The episode is available on YouTube and DVD.
The video worksheet is a one-page, double-sided handout consisting of 39 multiple choice questions that track the progress of the video. This format enables the students to pay attention to the video while quickly recording their answers. In this way, the students are not bogged down in writing long responses, and they can better enjoy watching the video. A key is included, and the files are provided in both MS Word and PDF formats.
History Channel’s How the Earth Was Made: Loch Ness Overview
In Scotland, Loch Ness is a 23-mile long, one-mile wide lake that is famous for its legendary monster. Today we know that the shape of the loch is dictated by an ancient fault line that became reactivated in recent years by the birth of the Atlantic Ocean. Loch Ness is just one of the myriad geological wonders of Scotland where some of the earth’s oldest rocks are found along with immense lava flows, extensive faulting, Jurassic age dinosaur fossils, and evidence of recent glaciation.
Many Scottish castles were constructed of material from a famous rock layer known as the Old Red Sandstone. This rock layer is contiguous in age and morphology to rock deposits in North America, in particular the Catskill Mountains. Amazingly, the brownstone buildings of New York City are made of the same rock as Scottish castles! The Old Red Sandstone is evidence of the interconnectedness of earth’s continents that was revealed by the theory of plate tectonics. Northwest Scotland and North America were once joined together as a continental land mass. In later earth history, northwest Scotland became separated from North America and welded onto the land of southeast Scotland and England.
The bedrock of northwest Scotland and Loch Ness consists of some of earth’s oldest rock, and dates back from 2.5 to 3 billion years. This ancient crust, part of earth’s first continental landmasses, can be found as outcrops in northwest Scotland. The oldest rock in this sequence is known as the Lewisian gneiss. In a roadcut documented in the video, the Lewisian gneiss is seen to have been subjected to numerous episodes of intrusion and burial. Younger black igneous rock and red granite intrusions are visible as a chaotic jumble in the roadcut. The only forces known to create such an assembly of rocks are the tectonic motions of earth’s plates. Eventually, this ancient crust became stable and formed a land surface. Much of the ancient crust was then eroded away into what geologists call an unconformity. Later in time, newer sedimentary rock layers were deposited atop the ancient crust. These younger rock layers, such as the Old Red Sandstone, were the products of river erosion.
This period of geologic calm, lasting nearly one-third of earth’s history, came to an end with the collision of Europe and North America that formed the Appalachian Mountains and other mountains in Europe. This collision, known as the Caledonian orogeny, significantly affected the rocky crust of Scotland and formed a series of faults. The Great Glen Fault in particular, which is responsible for the “straightness” of Loch Ness, formed at this time.
The Moine Fault, which is highlighted in the video, displays older Lewisian Gneiss atop younger sedimentary layers and represents a seeming contradiction of normal geological processes. In considering this paradox, Scottish engineer Henry Cadell provided an explanation for these types of extreme faults, now known as thrust faulting. Cadell didn’t know about plate tectonics, but he realized that an unknown horizontal force of compression had pushed older rocks atop younger rocks. As shown in the video, Cadell created a device that squeezed simulated rock layers in a horizontal manner, and was able to replicate the faults observed in nature.
The Isle of Skye in northwestern Scotland bears evidence of the motions of continents and earth’s past life. During the Jurassic period (201-145 million years ago), this part of the earth was located near the equator and had a tropical climate that featured dinosaurs. In 1994, an amateur geologist discovered fossilized tracks of the dinosaur Megalasaurus on Staffin Bay, Isle of Skye. As described in the video, Megalasaurus was a fierce Jurassic period predator. Examination of the tracks suggested that the animal was running and perhaps chasing prey. Other dinosaur discoveries on Skye include a fossilized Plesiosaurus skeleton, an aquatic reptile that some have linked to the mythical creature known as the Loch Ness Monster.
60 million years ago, Scotland became separated from North America by the birth of the Atlantic Ocean. Evidence for the emergence of the new ocean basin consists of immense lava flows seen in Scotland and Ireland. Many of these rocks display the amazing columnar basalt formations resembling giant crystals, and which form naturally in thick, slowly cooling lava. As indicated in the video, deposits of the ropey lava named pahoehoe indicate that the lava deposited in Scotland resulted from forces deep within the earth related to the formation of a new ocean basin. The Great Glen Fault became “reactivated” at this time due to the stresses involved with the formation of the Atlantic Ocean basin. This fault resembles a straight line, and can easily be seen on a map of northwest Scotland. It is a strike-slip fault similar to the San Andreas Fault in California, but is no longer producing strong earthquakes. This linear cut in the earth’s crust formed the underlying template for the unusually straight Loch Ness.
In more recent times, the earth entered a period of cooling climate that started about two-and-a-half million years ago. In this ice age, which is still occurring, the earth experiences colder temperatures about every 100,000 years, and the growth of continental glaciers is facilitated. These glaciers once extended into the Midwestern United States, as well as much of Europe. Much of Scotland was once positioned under hundreds of feet of glacial ice.
The ice ages were discovered by Swiss geologist Louis Agassiz who devoted his career to studying the features created by glacial ice, and he was able to correctly identify glaciers as the source of much of Scotland’s current topography. In 1840, Agassiz visited the Glen Roy Valley, which features unusual horizontal features known as “parallel roads” that run absolutely straight along the side of the valley for many miles. Charles Darwin had earlier surmised that the Glen Roy parallel roads had once been coastlines that were later raised by earthquakes-Darwin had noted such features in South America. Agassiz explained that the Glen Roy had been filled by a freshwater lake that had experienced different depths in the past. The parallel roads are the ancient coastlines of this vanished lake. The water had resulted from melting glaciers, and had been temporarily trapped in the valley.
Many of Scotland’s mountain valleys display the classic U-shaped profile of valleys scoured and eroded by glaciers. One such valley, Glencoe, is described in the video, and is notorious as the site of a famous massacre. Depth measurements of Loch Ness reveal that it also has the characteristic U-shape of a glacially scoured valley. The Great Glen Fault was the original foundation of the loch, and this weak point in the crust became eroded by glacial activity. The water in the loch was likely derived from melting glacial ice, and its exit was blocked by glacial deposits of rock and soil.
Concerning the legendary monster, we now know that the iconic photo was faked, and there is virtually no scientific evidence supporting the monster’s existence. As a body of water, the loch is a relatively recent feature at 10,000 years of age that resulted from the last glacial advance. It would be nearly impossible for a dinosaur from the Jurassic period, over 145 million years ago, to have somehow survived and later made its way into such a relatively young lake. The loch is just too young to have been able to support a holdover population of dinosaurs, and the Loch Ness Monster is most certainly a myth. Despite this conclusion, Scotland itself is a land of earth history wonders, and the country has had an important role in the history of geology.