"The rivers and the rocks, the seas and the continents have been changed in all their parts; but the laws which direct those changes, and the rules to which they are subject, have remained invariably the same." -From Charles Lyell's, The Principles of Geology, 1830.

Modern geologic theory, made famous by Charles Lyell in the 1830's in his journal called The Principles of Geology, was based on the premise that all things have changed, and will continue to change, and all things have done so and will do so under the same forces of nature. He conjectures that for millions of years, earthquakes, floods, volcanoes and the movement of the plates have caused the destruction and the formation of new mountains and land structures. This theory allowed the geologists to look at mountains for their rock structure, and relate different mountain ranges with one another, thus conjecturing about their ages. Lyell attempted to date the Alps, yet they never were able to ascertain the number of "different periods at which the Alps gained accessions to the height and width" (Lyell, 137). They were however able, because of modern theory, to derive the last series of movement, which he believed "occurred when seas were inhabited by many existing species of animals" (Lyell, 137).

Lyell discovered that glacial movements in these mountains have torn fissures, and continue to tear fissures, in the sides of mountains. "When valleys have become filled with ice, the contraction of the mass causes innumerable deep rents, such as are seen in the mer de glace on Mont Blanc..." (Lyell, 98). Like this lithograph of the Mer de Glace, near Mont Blanc, circa 1860, the fissures and broken rocks are seen, as well as the glacial ice cutting far back into the mountain.