Geological Revolution: Rocks Formation and Classification
US Geological History: Written in Stone
Northeastern United States geological history begins with the Precambrian Grenville rocks, which can be seen in the Adirondack mountains located in the northern New York state and also the syncline and anticline of the Green mountains Vermont. These rocks have a notable long Precambrian history, which brought them repeated layers of sedimentations after metamorphism, deformation and lastly intrusion. One of the major occurrence involved splitting of the continent that contained Green belt, which after drifting of the continent led to the emergence of both rift zones and oceanic basins. In the oceanic periphery, there are deposits of the late Precambrian, volcanic materials and early Paleozoic sediments.
It was in this period that the oceans began to narrow the gap due to deformation that is also known as Taconic orogeny. The latter typically involves the folding, uplift and down lift sliding’s, metamorphism and intrusion. Through these geological processes, some areas have been affected, including Northern Maine and New England. In a time known as the Devonian, there was a great metamorphism and a granite intrusion that led to the production of mountains; as the result, a delta was built in the deformed area.
The next geological recorded period involved warping and faulting, that led to sedimentation and volatile volcano eruptions in rift valley, thereby resulting in the production of deposits that are known as Triassic. It was in this period that the Atlantic Ocean opened, and the seawater moved to the eastern margin of the North American continent. Upon the opening of the Atlantic Ocean, it resulted in the production of volcanic calderas. These rocks were known as igneous, embracing both extrusive and intrusive specimens that were alkali in nature.
It was during the last geological period known as Pleistocene continental glaciation that raising and falling of oceanic level resulted in formation of glaciers. This process was accompanied by exposing of geological continental shelves and led to flooding of the coastal areas.
Overall, the chapter presented a brief overview of the crucial milestones in the history of landscape formation and change. According to Raymo, among these important ages are the following (2001):
1150-1050 Ma: Age of Grenville orogeny that resulted in the metamorphism of Adirondack Mountains
550 Ma: Deposition of Potsdam sands
500-460 Ma: Taconic orogeny
465 Ma: Cooling ages of Taconian orogeny
440-450 Ma: Intrusive rocks that collided during Taconian orogeny
400-380 Ma: Acadian orogeny
320-280 Ma: Alleghenies orogeny
220-180 Ma: Initiation of rifting of Atlantic
The Writing in the Stone
It was between these periods that tons of granite known as old man of the mountain had their grip loosen on the Cannon Mountains in New Hampshire; in the process, a lot of granites were crashed. It was attributed that old man of the mountain was irreversible work of God or rather nature. Indeed, in this period, the formation of granite appeared to be a wonder, as it was quite a rare outcome.
By the nineteenth century, geology as a science was assessing the immense age of the earth and assumptions that creation played immense part in history regarding formation of geological features, such as mountains. With these findings, Chet Raymo suggested that the Earth was probably seven thousand years old and accounted that the spiritual scriptures stored in fossils records were a considerable evidence of human evolution. By examining a new geological period known as the Azoic, the author claims that before the formation of any kind of life on the Earth, there were rocks that had no fossils in them.
These findings led to the classifications of rocks as follows:
1. Primary rocks were regarded as the oldest types of rocks that were not stratified in layers, had no fossils in them and were in most cases found in the mountainous areas.
2. The second type is known as secondary rocks, which are more recent as compared to primary rocks and contain fossils in them; they are also stratified in layers and in most cases found in the lower regions of the mountainous areas.
During freezing, there was formation of cracks broad enough to construct ridges. As the ice eventually melted, it largely exposed ridges’ walls, which were in a constant attack of the weather. As water sipped into the formed cracks, the ridges froze and thawed thus breaking pieces from the rock wall on top of the Cannon Mountains.
As falling blocks dropped from the top of the cliff to the ground, it led to the breaking of rocks into smaller structures that formed the Talus slope. It is referred to as the Jurassic period that resulted in a period of about 180 million years, where hot magma surrounded the New Hampshire.
To summarize, this chapter continued the topic of the previous one, namely the stages of landscape formation, and narrowed it down to the description of these landscapes’ structure. The section thereby dwelled on the processes that caused various types of rocks to appear, classified them and explained the meaning of such classification for the human history.
Laying in the Foundation
During the continental rifting, features such as Metcomet ridges and Mountain Holyoke probably took place more than 200 million years. It was the end of Triassic era, which is typically associated with drifting of the Northern American land to other continents of the Earth, such as Africa and Eurasia. During the volatile volcanic eruptions, there was formation of lava. After millions of years, the lava drifted away from the rifts and eventually solidified into uniform strata that were actually very thick.
Due to constant processes such as earthquakes, that involve shaking of the earth and faulting of the rocks, it caused tilting of the lava and subsequently creating features such as ridges and cliffs of Mount Holyoke.
Basalt is formed as the result of consistent massive flow of the lava. It is a dark volcanic rock that contains rich minerals supporting the growth of plants and animals’ survival. Erosions, especially during the rainy seasons, lead to the formation of sedimentary rocks due to the depositions of sediments, which are accumulated in between the basalt rocks.
Due to increasing rate of erosion, the sedimentary rocks wither quickly as compared to the basalt rocks. As the result, they leave behind basalt layers exposed and eventually cause creation of cliffs and ridges. In other situations, immense erosion and glacial processes lead to the formation of conglomerates that are seen in mountain masses.
The Metacomet Ridge boasts of a number of microclimates that are rare in the New England, as it offers support to the oak savannas. They are in most cases dominated by chestnut oaks and also contain a variety of grass and ferns. The Metacomet Ridge has Talus slope, which is very rich in calcium nutrients supporting plants. There are also ponds, dams and reservoirs in the rock ridges shelves, that are important in supporting aquifers and other habitats. Other ecosystems found in the Metacomet ridge include, for example, the Northern Riverine, which offers support to such species as American elm, sycamore and willow. Besides, cactuses have been observed in the south facing mountains similar to back slope plants adjacent to the plateaus in the Metcomet Ridge.
As is seen, the section “Laying in the Foundation” (Raymo & Raymo, 2001) focused not only on the formation of stones with the span of time, but on its direct consequences as well. That is, the authors lead the readers to a thought that certain geological processes did contribute to the development of a floral life; in other words, they lied in the foundation of it, which is implied by the chapter name.
The Taconic Upheaval
This chapter discusses the period that is commonly referred to as a mountain building that lasted 440 million years. Due to mountainous erosions, sediments from the mountain were spread to the Northern America and Appalachians. As the sea began to shut down, the heavy weight of sediments and natural compressing forces resulted in the eastern of the North American to fold downwards step by step.
It is evident that after consistent depositions, a way to soft fine layer of sediments and much deeper water situations was given during an era known as Middle Ordovician. As the result, convergent plate boundaries developed. After the subsiding of Taconic orogeny, culminating of sediments of the Iapetus’ terrain resulted in formation of huge mountains around New England and Northern America. As erosion continues taking away sediments from higher upland areas, the inland that covers middle continents expands eastwards thus the formation of shallow clastic and deposition of carbonates occurs.
Exotic Terranes, Green Terrain
It was until Ordovician era that New England was gradually placed together by the addition of North America continent. Those pieces of lands were known as exotic terrains; they had origins from North America and were held together when continents plates emerged together.
Earlier, during the mountain building also known as Taconic, volcanic features formed in the Iapetus Sea. During the emerging of plates, the murky oceanic crust of the Iapetus Sea was forced into the mantle where it is at last melted. As magma melts and the subduction of the crusted ocean occurs, the magma rises in between the plates to form a feature known as volcanic islands.
According to Raymo, it is evident that the exotic terrain has an origin in the African continent, as if it travelled from the south regions to the northern regions on plates that were already on motion, resulting in collision with the North America.
Terranes known as Iapetus and Avalonia, that make up the New England, were added to become a part of North east in a period of million years. It was during the Taconic and Acadian orogeny that they were collided, squeezed, squashed, misshaped and greatly metamorphosed. As the result, it became completely difficult to distinguish the formed features such as the volcanic islands that were joined together.
An African Affinity
It is during the stone age period where stones were used for various activities, such as making of weapons for defense purposes. It dates back to around 3.5 million years, even before the invention of metal working. The stone age is attributed to the evolution of the homo species, where it is believed that the cradle of human kind is attributed to be of East African origin and especially in the northern Ethiopia. Meanwhile, there was another group that are regarded as the closest relatives of the genus homo, who lived in the deeper forest.
During the stone age, it was not all about measuring the types of tools used, but also factors such as social and economic organisation, adapting to the climatic conditions, cooking, settling and also religion.The relationship formed a framework for the interaction of man and society.
Lithic analysis is an important form in geological investigations, as it helps in the measuring of tools and the resulting technology innovations.The three staged system was one of the greatest practises since it proposed a constant chronolgy of time that dated from early stone age to the late stone age.
During the three age system, adapting to the ideas of cultural anthropology and geology occurred, which described the ways of livings and certain believes that involved pratictising of stone age technology.
The three age chronology included:
-Lower paleothic perdiod, where soft pebbles were attributed to human ancestors that ranged 200000 years ago;
-Middle paleothic period, which is an era between 28000 years, where the Neanderthals lived across Europe and had immense relationship with archeological culture of Europe;
-Upper paleothic period, which ranged between 100000 and 50000 years; during this period, it led to end of paleistone and the emerging of Holocene era known also as the ice age era.
Birth of an Ocean
The Atchafalaya Basin is well recognized as the largest swamp in the Northern United States. It is located in South Central Louisisana, where it was formed as a result of converging of wetlands and a river delta, which are located where Atchafalaya and Mexico Gulf meets.
Atchafalaya Basin in United States has a permanent relationship with River Mississippi in a period known as Holocene epoch.The basin is as a result of deposital robes known as the sale-cyper mort, lafourche, and teche of the river mississippi and the geology of the basin has been propelled by flows of River Atchafalanya, and the resulting sediments are transported through the distributanary channels.
Atchafalaya Basin contains coastal deltas; as a result of building of flood controlling leeves, it leads to natural filling of the basin with full of sediments and other oceanic crysal fine rocks.
The basin is bordered by human made leeves that is projected to contain and direct floodwaters from River Mississippi towards Gulf of Mexico.Geologically, the Atchafalaya basin has an existing back swamp that lies in the low areas of the Mississippi through a process known as delta motion. During the mid ninenteeth century, after removal of a huge log jam and capabilities connecting the Atchafalaya and River Mississippi, the old river structure was completed as the River Mississippi largely diverted into the resulting basin.The expected flow and other deltas were to relieve the ever pressure on the leeves as a result, it helped immensely in flooding.
Atchafalanya has natural develpoments that assist in controlling floods and also in navigation purpose; as a result, it became an important distributor of River Mississippi.
Quiet Before the Storm
The chapter talks about geomagnetic storm affecting the earth magnetosphere that is caused by solar wind or a field of magnetics interacting with Earths magnetic field. The rapid increase in the solar wind pressure at first compresses the magnetosphere and, due to these interactions, causes growth in plasma movements, that passes through the magnetsophere and Ionesphere.
It is in the main phase of a geomagnetic storm that electric current creates a magnetic thrust that forces out the boundaries that separates the magnetosphere and the solar wind.Due to the temporary disturbance, the channel that takes the storm is maybe as a result of coronal mass ejection or the electric speed of the solar wind coming from areas of poor magnetic fields.
There are three phases of geomagnetic storm that include:
Initial phase: It is also reffered as storm sudden commencement, it is defined with Dst.
Main phase: It is categorized by reducing Dst in a duration of 2-8 hours.
Recovery phase: It is a geomagnetic storm that has a short period lasting eight hours or ten days.
Age of Ice
It is a period that is a result of significant reduction in the temperatures of the earth surface and the atmosphere. Due to reduction in temperatures, it leads to emergence of polar and continental ice sheets and also the alpine glaciers.The ice age period began probably 2.7 million years ago at the begining of the pleistocene epoch.
Ice ages have geological evidence that emerges in various forms, that include scrathing, glacial moraines, drumlins, valley cutting, and the deposition of sediments.There were five major ice ages on the Earth: Karoo, Huronian, Cryogenian, Andean-Saharan, and Quatemary glaciation.
- Huronian ice ages: They were formed around a billion years during the proterozoic era, they are found in the shores of Huron;
- Cryogenic period: Occurred between 630 to 850 million years, formed as a result of glacial sheets reaching the equator and also to accumulation of carbon dioxide and volcanoes;
- Andrean-Saharan: Occurred between 420 to 480 million years during the period of Ordovician and Siluriam;
- Quatemary period: Occurred about 2.58 million years ago during the pilocene, an era that was characterised by spreading of the ice sheets in the Northern Hemisphere;
- Devonian period: It was as a result of positive increase in oxygen and negative decrease in carbon dioxide which led to the formation of karoo ice ages.
Ice ages can be distinguished if the temperature is examined, the colder periods are known as glacial periods while the warmer periods are known as interglacials.
Going with the Grain
Almost all rocks are made up of tiny particles. It is observed that some rocks are homogeneous in nature meaning the grains of the rocks are the same in size and texture while others are heterogenous in nature meaning the particles are of different sizes and not of the same texture. These small pieces are known as grains,they come from different types of rocks.
These rocks include:
- Igneous rocks which are crystal like and they grow as a result of magma cooling
- Sedimentary rocks that have grains of sand embroided together by natural cementation.
- Metamorphic rocks are formed having been put to immense heat, pressure and chemical reactions.
Grains have distinct chemical compositions and are of different colours, examples, as the rusted metal.When grains are of similar colurs it is evident that they bear same geological history,these grains on the exposure of oxgen in air and water rust in a process known as chemical weathering.
Grains shape help us to determine the mechanical weathering history. This is because as rocks tear up, they form small sharp pieces which in most situations are angular in nature.As time progresses they get worn out by natural factors such as wind, water and other rocky materials.Most of these grains are categorised according to their roundness.Rocks are transported by wind, water, glaciers in the process they experience friction during collision with other features and thus experience mechanical weathering.
Rounded rocks are most vulnerable to mechanical weathering, this is because apart from them travelling longer, they have been developed in millions years in areas wth constant rubbing and abrasion with other rocks.
Although the grains are tiny, the sizes of distinct small particles differ. This is because it requires a significant amount of energy to move a larger grain, which exceeds the energy required to displace a smaller one.