The Shaping of Earth
The image of Earth from space is one of striking beauty; the mixture of blue, green, and white illustrating water, land and weather against a black backdrop. The Earth is about 4.5 billion years old, and looks very different than it did at its birth. Many geological processes have shaped the Earth’s surface, and continue to do so even today.
What Processes Shaped Earth?
During planetary forming, all planets were hit with fragments of broken planetesimals. This is evident from the cratering on the moon, which remains very much in tact due to its lack of atmosphere and other geological forces. Many of these impacts were so large that any present life would have be at significant rock of obliteration (Than 2006). Other later, significantly sized impacts are attributed to the extinction of dinosaurs. Evidence on Earth of these impacts is very limited because other geological processes continuously reshaped the surface, erasing many them. There are some that remain, such as the Sudbury Basin in Ontario, Canada. This crater is approximately 1.8 billion years old, and is the second largest crater found on Earth, measuring about 93 miles across (Ghose 2014). Impacts this large (or larger) not only shape the area they hit, but have extensive reach in remodeling because of the debris they scatter as well.
The Institute of Physics asserts that when an asteroid hits Earth, there is a significant transfer of kinetic energy to the Earth (2012). In Earth’s early stages, heat was a critical driving force of other geological processes, especially tectonics. While the energy transfer from impacts may not have been the sole cause of kinetic energy in Earth, it was definitely a contributing factor.
Erosion is the process of the wearing away of rock or ground via water. As water vapor became liquid and rained down onto the surface in early years, evidence of impact crater was worn down and in the case of smaller craters, washed away. Erosion is also responsible for shaping landscapes in the form of rivers and flooding. We currently see examples of erosion in the present, as this is a frequent and ongoing geological process.
This is somewhat unique in our solar system, as Earth is the only terrestrial planet that currently exhibits flowing water. While none of the other terrestrial planets currently have liquid surface water, there is evidence that at one time it did exist at least on Mars. Water in other states, and potentially underground, is present in other terrestrial planets. This is important because liquid water is a critical component to the process of erosion.
Another process that is responsible for the frequent reshaping of the Earth’s surface is volcanic activity. The type of volcano and lava has significant impact of the changes that occur. Volcanic activity is responsible for the creation of some plains, volcanic mountains, and the erasing of impact craters. Because the initial atmosphere of Earth was likely a hydrogen and helium mixture, volcanic activity significantly contributed to changes in the early atmosphere by allowing the release of oxygen; this greatly aided the potential for life because it facilitated water.
Tectonics is the term given to the process of building up surface features through certain geologic forces affecting the lithosphere. Tectonic changes can occur in many ways, both from the interior and exterior. The most significant tectonic impact is plate tectonics.
Plate tectonics are unique to Earth, and are the result of convection in the Earth’s mantle. They refer to the idea that ‘plates’ reside over the mantle, and move over and under each other causing changes to the Earth’s surface and physical features (Oskin 2016). This idea was originated by Alfred Wegener in 1912; commonly known as the continental drift theory, it explained that the continents had moved from an original position which all were close together (Oskin 2016). While these plates generally move very slowly, they are constantly moving and shaping the planet.
The movement of these plates explains much of Earth’s features as well as some geological events. For example, earthquakes are a result of tectonic plate movement. The edges of two adjacent tectonic plates form fault lines. Earthquakes occur when these two plates do not easily slide past each other. Another significant result of tectonics is seafloor recycling. This occurs when seafloor plates, which are less dense, move under continental plates; a trench is created which then allows seafloor to melt, and the melted material is then pushed through ocean floor ridges creating new seafloor (Oskin 2016). This process is called subduction, and is responsible for a great deal of remodeling on Earth.
Many of the geological processes that occurred within early Earth significantly contributed to the rise of life. Today, mankind impacts the surface of Earth through man-made impacts, though not nearly as significant as the ones that occurred during bombardment. Mankind also significantly contributes to the process of erosion because we attempt to manipulate natural features for our own reasons, and because our presence impacts weather patterns. Global warming may have an impact on volcanic activity as it is a way to cool the Earth; and it is undeniable that humans have significantly contributed to global warming. While mankind alone is not a geological process, we do contribute significantly to geological processes
Earth today is very different than Earth 100 million years ago, as well as compared to 200 million years ago and 1 billion years ago. There are new peaks and land positions. There are many different types of life. There are parts of Earth that no longer exist. In another billion years, Earth will again look very different than it does now. Geological processes continuously reshaping and change the Earth’s surface.