Climate of North and South America

Lesson 1: Continental Drift Theory and the Evidences that support the Theory Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics. The theory of continental drift is most associated with the scientist Alfred Wegener. In the early 20th century, Wegener published a paper explaining his theory that the continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other. He called this movement continental drift. Pangaea Wegener was convinced that all of Earth’s continents were once part of an enormous, single landmass called Pangaea. Wegener, trained as an astronomer, used biology, botany, and geology describe Pangaea and continental drift. For example, fossils of the ancient reptile mesosaurus are only found in southern Africa and South America. Mesosaurus, a freshwater reptile only one meter (3.3 feet) long, could not have swum the Atlantic Ocean. The presence of mesosaurus suggests a single habitat with many lakes and rivers. Wegener also studied plant fossils from the frigid Arctic Archipelago of Svalbard, Norway. These plants were not the hardy specimens adapted to survive in the Arctic climate. These fossils were of tropical plants, which are adapted to a much warmer, more humid environment. The presence of these fossils suggests Svalbard once had a tropical climate. Finally, Wegener studied the stratigraphy of different rocks and mountain ranges. The east coast of South America and the west coast of Africa seem to fit together like pieces of a jigsaw puzzle, and Wegener discovered their rock layers “fit” just as clearly. South America and Africa were not the only continents with similar geology. Wegener discovered that the Appalachian Mountains of the eastern United States, for instance, were geologically related to the Caledonian Mountains of Scotland. Pangaea existed about 240 million years ago. By about 200 million years ago, this supercontinent began breaking up. Over millions of years, Pangaea separated into pieces that moved away from one another. These pieces slowly assumed their positions as the continent we recognize today. Today, scientists think that several supercontinents like Pangaea have formed and broken up over the course of the Earth’s lifespan. These include Pannotia, which formed about 600 million years ago, and Rodinia, which existed more than a billion years ago. Tectonic Activity Scientists did not accept Wegener’s theory of continental drift. One of the elements lacking in the theory was the mechanism for how it works—why did the continents drift and what patterns did they follow? Wegener suggested that perhaps the rotation of the Earth caused the continents to shift towards and apart from each other. (It doesn't.) Today, we know that the continents rest on massive slabs of rock called tectonic plates. The plates are always moving and interacting in a process called plate tectonics. The continents are still moving today. Some of the most dynamic sites of tectonic activity are seafloor spreading zones and giant rift valleys. In the process of seafloor spreading, molten rock rises from within the Earth and adds new seafloor (oceanic crust) to the edges of the old. Seafloor spreading is most dynamic along giant underwater mountain ranges known as mid-ocean ridges. As the seafloor grows wider, the continents on opposite sides of the ridge move away from each other. The North American and Eurasian tectonic plates, for example, are separated by the Mid-Atlantic Ridge. The two continents are moving away from each other at the rate of about 2.5 centimeters (1 inch) per year. Rift valleys are sites where a continental landmass is ripping itself apart. Africa, for example, will eventually split along the Great Rift Valley system. What is now a single continent will emerge as two—one on the African plate and the other on the smaller Somali plate. The new Somali continent will be mostly oceanic, with the Horn of Africa and Madagascar its largest landmasses. The processes of seafloor spreading, rift valley formation, and subduction (where heavier tectonic plates sink beneath lighter ones) were not well-established until the 1960s. These processes were the main geologic forces behind what Wegener recognized as continental drift.

Continental Drift Theory. From the discussion of the rock cycle, it has been pointed out that through Earth's external and internal processes. Earth's surface is constantly changing. However, this idea of a changing environment did not conform with the belief of earlier scientists. Rather, they thought that the geographic positions of ocean basins and continents have been static since the beginning of time. It was around the 1500s when Leonardo da Vinci, upon his discovery of fossil seashells found at the high mountains of Italy, first thought of the idea that the areas where mountains are located may have been oceans in the past. Through time, other fossils of marine organisms found far above the current sea level further supported the idea that mountains were uplifted and weathering wore them down. At around the 1800s, most scientists have accepted the idea that Earth's crust is undergoing large vertical movements or uplifting. There was also evidence of possible horizontal movements, but the scientists then were not convinced about it. Alfred Wegener showed evidence of horizontal or lateral movement of the continents in his continental drift theory. According to him, the continents have drifted around the world and have once formed a giant landmass or supercontinent called Pangaea. To support his theory, Alfred Wegener presented a set of geographical, biological, and climatic evidence.Wegener's geographical evidence included the jigsaw puzzle fit of the current continents. He pointed out that the coastlines of South America and Africa seem to fit together. He also pointed the presence of mountain ranges having similar rock types and age but separated by vast oceans, like that of the folded rocks of the Caledonian mountains. The same folded rocks run through West Africa, North America, Newfoundland, Ireland, Wales, Scotland, Greenland, and Norway, all of which are now separated by the Atlantic Ocean. A geographical evidence on the similar rock types in West Africa, North America, Greenland, and Europe is found. The biological evidence came in the discovery of similar plant and animal fossils in different continents separated by oceans. The animal fossils of Mesosaurus and Lystrosaurus indicate that they were not capable of crossing the oceans to reach the other continents. If they were, the fossils should have been more widely distributed Africa, Australia, India, and South America were too large to be carried by wind. This indicates that the areas where the fossils were found were closely linked. It has also been found out that the plant only grew in areas with subpolar climate, which would indicate that the landmasses were located near the South Pole.Lastly, for his climatic evidence, Wegener discovered that a glacial period occurred during the late Paleozoic era in Southern Africa, South America, Australia, and India. The initial explanation for this event was global cooling, but it was rejected because large tropical swamps with so much vegetation were found at the same time in the Northern Hemisphere. This further supported the idea that the supercontinent was indeed near the South Pole, and the continents in Northern Hemisphere were once near the equator. The glacial period also left glacial striations, or the scratches glaciers make as they move across on the underlying bedrock, on the aforementioned continents. For such an event to happen, the continents would have to be connected. SCIENCE PIONEER. Alfred Wegener (1880-1930). Alfred Wegener was a German polar researcher, geophysicist, and meteorologist. He was known for his work on the continental drift theory. In his effort to defend his work, he went to the Greenland ice sheet where he died.Even with all the compelling evidence, the continental drift theory hardly convinced the scientific community at that time because Wegener was unable to identify a credible mechanism that drives the continental drift. He was unable to clearly explain how the continents moved and how the larger continents broke through the ocean floor. Eventually, critics of the continental drift began to accept the theory when new evidence supporting the theory was discovered. The new evidence led to a more encompassing theory the theory of plate tectonics. This theory provided a more convincing explanation as to how the continents moved. The evidence that paved the way for the theory of plate tectonics was the idea of wandering poles. Scientists began studying volcanic rocks to determine the location of the magnetic poles. When volcanic rocks crystallize, the minerals with magnetic properties align themselves parallel to Earth's magnetic field at the time the minerals were formed. This finding allowed scientists to determine the polarity of Earth's magnetic field and the magnetic inclination that showed the location of the poles. Upon studying the paleomagnetism of the rocks, geophysicists found out that rocks from various locations point to different magnetic north poles, suggesting that the poles have wandered. Since movement of magnetic poles is very unlikely, scientists have accepted the idea that the continents are indeed moving. And if the continents are moving, scientists thought that maybe the ocean basins are moving too. They also discovered that some rocks showed magnetic reversals, which led them to believe that the magnetic north pole now was not always the magnetic north pole. Seafloor Spreading. After World War II, exploration on the ocean floor became the focus of many geologic studies. It was only then that the ocean ridge system was discovered. A geologist in Princeton University named Harry Hess, along with other scientists, studied this ocean ridge system and hypothesized that the oceanic crust was moving away from the ridge. His hypothesis, known as seafloor spreading, showed that the ocean floor is split along the ridge where the magma rises to form the new ocean floor.Because of this, rocks located near the ridge are younger than those that are located magnetic polarity of Earth is also preserved in those rocks. Withe ridge scientists were able to see the magnetic reversals in the ocean floor, and they were able to make use of information to determine that the ocean floor is moving at a rate of about 10 cm per year. Plate Tectonics. Confirmation of the seafloor spreading hypothesis proved that continents are not moving above the ocean floor. Rather, it is the fragments of the lithosphere. The lithosphere is the rigid layer that is composed of the uppermost mantle and the crust that carry the continents and the ocean basins along. These fragments of the lithosphere are called plates. Underneath the lithosphere is a weaker region in the mantle known as asthenosphere that behaves like a fluid. Thus, the lithosphere floats above the asthenosphere, making it detached and free to move. This became the basis of the theory of plate tectonics. Now that it has been made clear that it is the plates which are moving, the question as to how they move remained. Sir Arthur Holmes proposed the driving force for this plate movement in 1919. He suggested that the movement in the mantle carries the plates along. It was previously discussed that Earth's interior is very hot due to the heat produced by radioactive decay. Convection takes place in the mantle, keeping the asthenosphere hot and weak. The convection currents produced in the asthenosphere are the ones carrying the lithospheric plates and making them move. However, convection currents are not enough. Mechanisms such as ridge push and slab pull aid the convection currents to slowly move the lithospheric plates. Ridge push occurs at mid ocean ridges which are higher in elevation than the surrounding trenches and abyssal plains. The new ocean floor from the ridge is hot and relatively thin. As it moves away from the ridge, it cools down and gets denser, heavier, and thicker. Below this cooling ocean floor is the asthenosphere, which is less dense. This area becomes a massive shear zone and the new ocean floor will effectively slide down the slope of the asthenosphere. When the plate collides with another plate with lesser density, the denser plate sinks and a subduction zone is formed. When the subducting plate sinks, it pulls on the rest of the plate behind it. These mechanisms explain the movement of the plates.Earth has seven major lithospheric plates that account for 94% of Earth's surface. These are the North American Plate, South American Plate, Pacific Plate, African Plate, Eurasian Plate, Indo-Australian Plate, and Antarctic Plate. These plates are constantly moving relative to the other plates. Thus, the interaction of plates occurs mostly along the boundaries. These movements are plotted using information from earthquakes and volcanic activities. There are three main types of plate boundaries: convergent, divergent, and transform boundaries Convergent boundaries are boundaries where two plates move towards each other A convergent boundary is also known as destructive margin since this is where the collision between two plates occhins. There are three types of convergence-oceanic oceanic, oceanic-continental, and continental-continental. Trenches are features of the ocean floor that are present in both oceanic-oceanic boundary and oceanic-continental boundary. Subduction occurs at the trenches, therefore, these are characterized as the deepest parts of Earth. A divergent boundary is the opposite of convergent boundary: two plates move away from each other. Divergent boundaries create new crust; thus, they are also known as constructive margins. The ocean ridge system is a divergent boundary where new ocean floor is produced as magma rises, pushing the older rocks aside.Transform boundary is also known as conservative plate margin since two plates just move past one another, neither creating nor destroying land. Earthquake epicenters are usually detected at transform boundaries because the rocks tend to break and not fold or sink, like in convergent boundaries. Evolution of the Ocean Basins. Both the movement of the plates and seafloor are responsible for the evolution of ocean basins. Along the divergent boundary where ocean ridge systems are found, magma is released and new ocean floor is created. Along convergent boundaries, the ocean floor is being destroyed. The evolution of the ocean basins started during the time when Pangaea was still present and was surrounded by the vast ocean or superocean known as Panthalassa, also called Paleo-Pacific or "old Pacific." Upon the initial break up of Pangaea into Laurasia and Gondwanaland, the Tethys Sea began to form. Then, the Eurasian and North about, forming the North Atlantic. The South Atlantic only started to form when the African Plate and South American Plate separated. The continued movement of the plates created the Himalayas at one side and separated the Pacific Ocean and Atlantic Ocean at the other side, which consequently formed the current ocean basins. Both the movement of the plates and seafloor are responsible for the evolution of ocean basins. Along the divergent boundary where ocean ridge systems are found, magma is released and new ocean floor is created. Along convergent boundaries, the ocean floor is being destroyed. The evolution of the ocean basins started during the time when Pangaea was still present and was surrounded by the vast ocean or superocean known as Panthalassa, also called Paleo-Pacific or "old Pacific." Upon the initial break up of Pangaea into Laurasia and Gondwanaland, the Tethys Sea began to form. Then, the Eurasian and North about, forming the North Atlantic. The South Atlantic only started to form when the African Plate and South American Plate separated. The continued movement of the plates created the Himalayas at one side and separated the Pacific Ocean and Atlantic Ocean at the other side, which consequently formed the current ocean basins.Continents do not immediately end at the point where the ocean meets the land. They may extend slightly into the oceans. The portion of the continent that is submerged is called continental margin. There are two types of continental margin: passive margin and active margin. A passive continental margin consists of a continental shelf, continental slope, and continental rise. It is not associated with plate boundaries; thus, there are very little tectonic activities. An active continental margin only has a continental shelf and a continental slope. It is associated with plate boundaries; thus, a main feature of this boundary is a trench. The different features of a continental margin are the following: 1. The continental shelf is the gently-sloping submerged portion of the continent. 2. The continental slope is the steep slope after the continental shelf. It is still part of the continent. 3. The continental rise is the gently-sloping area after the continental slope and before the ocean floor. 4. The trenches are the deepest parts of the ocean. These are narrow depressions caused by the subduction of the ocean floor along the convergent boundaries. 5. The mid-oceanic ridge is the mountain range system in the ocean. It is responsible for the production of new ocean floor. This is the region where new magma constantly emerges from. SCIENCE CAREER. A scientific illustrator uses art to inform and communicate complex details and concepts of science. He/She makes use of scientifically informed observations and research along with his/her technical art and aesthetic skills to make accurate representations. In Natural History, the scientific illustrators recreate how the extinct species look like by working with scientists and fossil records. Moreover, with the advances in technology, illustrators are now into 3D modelling, animation, and video making. Earth's History. All the processes that have been discussed require long periods of time to create a noticeable change on Earth's surface. You can just imagine how long it would take to create an oceanas vast as the Pacific Ocean if the ocean floor moves only at about 10 cm/year. It is then important to know the history of Earth to learn the complexities of its past and be able to use it to understand the present. Just like learning the history of a country that requires one to read a lot of books, learning the history of Earth involves studying a lot of rocks. Rocks, especially sedimentary rocks, contain a lot of information about Earth's past. It holds the key to most of the geologic processes that happened on Earth and the key to uncovering how life on Earth evolved. But these discoveries are worthless if there is no time perspective. Thus, one of the most important contributions of geologists to mankind is the geologic time scale, which holds a history that is exceedingly long.

Think about the geography and location of the city or town you live in. Are there bodies of water like rivers and lakes or a coast nearby? Perhaps you live in a place with vast open fields suitable for farming or raising livestock. The natural environment is important when understanding how cities and towns developed. The earliest North American colonies depended on their natural environment. The type of soil, climate, length of seasons, and proximity to bodies of water all played a role in how each colony prospered. By the 1700’s, the American colonies grew into three distinct regions. The New England, Middle, and Southern regions each had different geographical and cultural characteristics that determined the development of their economy, society, and relationships to each other. The New England Colonies included Connecticut, Rhode Island, Massachusetts, and New Hampshire. The geography of this region featured dense forests and hills. Combined with the hard rocky land, cold climate and long winters, New England was a poor area for large farming operations. However, many colonists known as "yeoman farmers" had small family-owned farms that grew a variety of crops. Many other colonists relied on fishing and whaling off the New England coast. Others settled in small towns and became craftsmen or merchants. The forests provided excellent lumber for building boats and homes for the growing population. Many of the settlers to the New England Colonies were Puritans, hardworking, and very religious. Close families and strong communities were very important to them. The Middle Colonies included Pennsylvania, Delaware, New York, and New Jersey. The geography of this region featured a warmer climate with fertile soil, flat land, easily navigable rivers, and wide valleys making it perfect for farming and growing crops. Wealthy farmers grew cash crops and raised livestock. Mining and trading were also important aspects of the economy here. Over time, cities grew, and urban merchants sold and traded goods with people throughout the other colonies. Compared to other regions, the people of the middle colonies supported religious freedom and tolerance and had a diverse population with settlers arriving from many areas in Europe. The Southern Colonies included the first English colony of Virginia, and grew to include Maryland, North Carolina, South Carolina, and Georgia. The geography included rich, fertile soil with broad coastal plains that made it possible for large plantations to grow tobacco, rice, and indigo. Most of these plantations featured a labor force of enslaved Black people. These enslaved men, women, and children had few, if any, rights and often saw their families torn apart at the whim of the plantation owner. Enslaved children were even put to work as young as age three, weeding fields, carrying drinking water, or helping in the home. Smaller farms owned by subsistence farmers also existed across the Southern Colonies. Often, the people working these would grow crops for their families with little left over to sell or trade. Indentured servants also arrived in the South who would work for 5-7 years in exchange for their passage to North America. The Church of England (also known as the Anglican Church) was the dominant religion in the region. Most settlers to the South did not come for religious freedom like they did in the northern colonies. Therefore, they often maintained their allegiance to the established Church of England.

Chapter 8: The Worlds of North and South Geography Geography refers to the seasons, climate, soil, and physical features of a region (mountains, rivers, etc.) The differences in geography b/t the N and S is one of the major reasons slavery b/c entrenched in the S while it died out in the N. Geography of the North The N has diverse geography and experiences four distinct seasons including long, harsh winters. The Great Plains region has some of the best farmland in the country. New England has rocky, hilly wilderness, not well suited for farming. It has hundreds of bays and harbors along its coastline. States farther S had rich soil and coastal access through rivers. The N also experienced mass deforestation b/c of the need for lumber and to make room for farms. Geography of the South Climate: the S had mild winters, and a long, hot, humid growing season. It has fertile lowlands, marshes and swamps. It's ideal for growing tobacco, sugar, rice, indigo, and cotton (cash crops). B/c of the geography of the S, their whole way of life was based on agriculture and geography is one of the major reasons why slavery took off in the S. Economies Economy basically refers to the way people make and spend money. The Northern economy was far more diversified than the Southern. Economy of the North The North experienced the Industrial Revolution—the shift from handmade goods to machine-made goods. This resulted in new jobs, increased production, and improved efficiency in agriculture. IOW, you can make things faster, easier, and cheaper. More ppl get more stuff. Factories were almost always located next to rivers. The Reaper The Indust. Rev. changed northern agriculture with Cyrus McCormick’s reaper. It could cut 28xs more grain than a single man. The Sewing Machine Elias Howe's sewing machine; At 250 stitches a minute, Howe's lockstitch mechanism out-stitched the output of five hand seamstresses with a reputation for speed, completing in one hour what took the sewers 14.5 hours. The Textile Mill Francis Cabot Lowell's textile mill: essentially the first factory in the US, Lowell set the model for all future factories. Interchangeable Parts Eli Whitney's interchangeable parts; considered the "dawning of a new age" of machinery. This concept was applied to pretty much all manufacturing. Economy of the South The South's economy was based on AGRICULTURE. Most southerners were agrarians. Most had small farms, some owned plantations. Slavery beginning to decline in late 1700s; prices went down (tobacco, indigo) and cotton was difficult. King Cotton Cotton was South’s most important crop. Earned more money than all other exports combined. The S would go on to supply 75% of the world's cotton demand. Cotton Gin Eli Whitney invented the cotton gin in 1794 and forever changed the US. The gin made cotton incredibly profitable. We start to see the effects of the cotton gin around 1820. Slavery and Cotton Southerners put all their money into slaves and land, and almost none into building factories. With the spread of cotton, demand for slaves increased. 1790 to 1850, number of slaves rose 600%. Transportation Again, the N was far more inventive in their approach to transportation than the S. Transportation in the North National Road National Road stretched from the East (the Potomac), over the Appalachians, to the West (Illinois), over 620 miles. Steamboat In 1807, Robert Fulton invented the steamboat. It traveled 150 miles UP the Hudson River at a speed of 5 mph. Erie Canal Built b/t 1817 and 1825, the canal spanned 363 miles and connected Lake Erie to the Hudson River. This connected farms in the W to cities in the E and the Atlantic Ocean. Clipper Ship Clippers were narrow w massive sails that were built for speed. They cut the time it took to cross the Atlantic in half. Locomotive The fastest and cheapest way to move goods was by steam-powered trains. The first RR was the B&O which was built in 1827. Transportation in the South Most people and goods in the South traveled by rivers in steamboats. The South had trains, but less than half the amount of railroad track than the North had. Society (The People) The people who made up the N and S could not have been more different. The S was primarily agrarian while the N was b/c urbanized. The S was holding on to the past, while the N was embracing change. Society in the South Society was organized into 3 distinct classes of people: rich plantation owners at the top; then white farmers and workers; slaves on the bottom. This rigid social class system was the result of a slave-based agricultural system. Power Structure Only 1 in 4 whites owned a slave. Plantation owners, who owned more than 20 slaves, dominated politics and the economy. Society in the North 7 of 10 Northerners still lived on farms by the 1840s (6 of 10 by 1860), but urbanization was growing fast in the N. The N relied on wage labor as opposed to slave labor, so most blacks in the N were free. N blacks were not treated equally and the N was about as racist as the S. Immigration Compared to the S, the N population was exploding, in large part bc of immigration. Between 1845 and 1860, 4 million immigrants came to the North. Most were German and Irish. Irish--a potato famine; German--a failed revolution. Ethnic neighborhoods developed as a result.

Geography: the study of Earth’s physical and cultural features Landforms: the natural features of the land’s surface Climate: the average weather conditions in a certain area over a long period of time Environment: All the living and nonliving things that affect life in an area Region: An area with one or more features that make it different from other surrounding areas Map Key / Map Legend: box that explains the meaning of different symbols used on the map Map Scale: tool that measures the relationship between the distance of locations on the map and the distance of locations in real life Compass Rose: a circle that shows the key directions on a map Hemispheres: halves of the Earth Continent: one of seven large landmasses on Earth Oceans: large bodies of water that cover 71% of the Earth’s surface Latitude: imaginary horizontal lines that measure distance north and south of the Equator Equator: central line of latitude that is measured at 0° Longitude: imaginary vertical lines that measure distance east and west of the Prime Meridian Prime Meridian: the central line of longitude, which is measured at 0° and runs through Greenwich, United Kingdom Map: illustration of a specific area on Earth that is often portrayed on a flat surface Physical Map: a type of map that shows the natural landforms and terrain of a location Political Map: a type of map that identifies cities, states, and countries Globe: a spherical model that is the most accurate representation of Earth

air mass a large area of air that has uniform temperature, humidity, and pressure. air pressure the force that a column of air applies on the air or a surface below it albedo the measure of the sun's reflectivity on Earth's different surfaces atmosphere the layers of gases surrounding Earth climate average weather conditions in a specific region over a long period of time coriolis effect the movement of wind or currents in a curved path due to Earth's rotation eddy Smaller, temporary loops of swirling water that can travel long distances before dispersing front a boundary between two air masses greenhouse gas a gas in the atmosphere that absorbs part Earth’s outgoing infrared radiation gyre a large circular system of ocean currents. humidity the amount of water vapor in the air hydrosphere system containing all the solid and liquid water on Earth jet stream Narrow bands of high speed wind high in the troposphere that move from west to east land breeze Winds that blow at night from land toward the sea. This is due to the fact that land has a low specific heat capacity and cools faster than water. This creates high pressure over the land at night and thus wind. local winds Winds that blow over short distances polar easterlies cold winds that blow from the east to the west near the North Pole and South Pole. prevailing wind distinct wind patterns caused by differences in pressure and the Coriolis effect sea breeze Winds that blow during the day from the sea toward land. This is due to water having a high specific heat capacity and it does not heat or cool quickly. High pressure then forms over the water during the day and blows toward the land. specific heat capacity The amount of heat that must be added to a substance to increase the tempurature by one degree Celsius storm surge water that has blown outward from the center of a tropical cyclone or hurricane and creates an abnormal rise in ocean waters on the coast surface current Currents near the surface of the ocean. Driven by wind, the Coriolis effect, and continental deflection trade winds Steady winds that flow from east to west between 30°N latitude and 30°S latitude along the equator tropical cyclone a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters typhoon a tropical cyclone occurring in the Pacific Ocean; especially in the region of the Philippines or the China Sea. weather the short-term atmospheric conditions in a given place and time westerlies steady winds that flow from west to east in the middle latitudes (30- 60 Degrees). These impact our weather in the US. wind shear A large shift in wind speed and

Soils Southeast Asia, on balance, has a higher proportion of relatively fertile soils than most tropical regions, and soil erosion is less severe than elsewhere. Much of the region, however, is covered by tropical soils that generally are quite poor in nutrients. Often the profusion of plant life is more related to heat and moisture than to soil quality, even though these climatic conditions intensify both chemical weathering and the rate of bacterial action that usually improve soil fertility. Once the vegetation cover is removed, the supply of humus quickly disappears. In addition, the often heavy rainfall leaches the soils of their soluble nutrients, hastens erosion, and damages the soil texture. The leaching process in part results in laterites of reddish clay that contain hydroxides of iron and alumina. Laterite soils are common in parts of Myanmar, Thailand, and Vietnam and also occur in the islands of the Sunda Shelf, notably Borneo. The most fertile soils occur in regions of volcanic activity, where the ejecta is chemically alkaline or neutral. Such soils are found in parts of Sumatra and much of Java in Indonesia. The alluvial soils of the river valleys also are highly fertile and are intensively cultivated. Climate All of Southeast Asia falls within the warm, humid tropics, and its climate generally can be characterized as monsoonal (i.e., marked by wet and dry periods). Changing seasons are more associated with rainfall than with temperature variations. There is, however, a high degree of climatic complexity within the region. Temperatures Regional temperatures at or near sea level remain fairly constant throughout the year, although monthly averages tend to vary more with increasing latitude. Thus, with the exception of northern Vietnam, annual average temperatures are close to 80 °F (27 °C). Increasing elevation acts to decrease average temperatures, and such locations as the Cameron Highlands in peninsular Malaysia and Baguio in the Philippines have become popular tourist destinations in part because of their relatively cooler climates. Proximity to the sea also tends to moderate temperatures. Precipitation Much of Southeast Asia receives more than 60 inches (1,500 millimeters) of rainfall annually, and many areas commonly receive double and even triple that amount. The rainfall pattern is distinctly affected by two prevailing air currents: the northeast (or dry) monsoon and the southwest (or wet) monsoon. The northeast monsoon occurs roughly from November to March and brings relatively dry, cool air and little precipitation to the mainland. As the southwestward-flowing air passes over the warmer sea, it gradually warms and gathers moisture. Precipitation is especially heavy where the airstream is forced to rise over mountains or encounters a landmass. The east coast of peninsular Malaysia, the Philippines, and parts of eastern Indonesia receive the heaviest rains during this period. The southwest monsoon prevails from May to September, when the air current reverses and the dominant flow is to the northeast. The mainland receives the bulk of its rainfall during this period. Over much of the southern Malay Peninsula and insular Southeast Asia there is little or no prolonged dry season. This is especially marked in much of the equatorial region and along the east coast of the Philippines. While the dry and wet monsoons are important in explaining rainfall patterns, so too are such factors as relief, land and sea breezes, convectional overturning and cyclonic disturbances. These factors often are combined with monsoonal effects to produce highly variable rainfall patterns over relatively short distances. While many of the cyclonic disturbances produce only moderate rainfall, others mature into tropical storms—called cyclones in the Indian Ocean and typhoons in the Pacific—that bring heavy rains and destruction to the areas over which they pass. The Philippines are particularly affected by these storms. Plant life Tropical forests in Southeast Asia Tropical forests in Southeast Asia The seasonal nature and pattern of Southeast Asia’s rainfall, as well as the region’s physiography, have strongly affected the development of natural vegetation. The hot, humid climate and enormous variety of habitats have given rise to an abundance and diversity of vegetative forms unlike that in any other area of the world. Much of the natural vegetation has been modified by human action, although large areas of relatively untouched land still can be found. The vegetation can be grouped into two broad categories: the tropical-evergreen forests of the equatorial lowlands and the open type of tropical-deciduous, or “monsoon,” forests in areas of seasonal drought. The evergreen forests are characterized by multiple stories of vegetation, consisting of a variety of trees and plants. Although a large diversity of tree species is found in these forests, members of the Dipterocarpaceae family account for roughly half of the varieties. Deciduous forests are found in eastern Indonesia and those parts of the mainland where annual rainfall does not exceed 80 inches. Just as in the equatorial forest, a wide variety of species is normally the rule. Certain species, such as teak, have become highly valued commercially. Teak is found in parts of Indonesia, Myanmar, Thailand, and Laos. In addition to these two basic types of vegetation, other regional patterns reflect topography. Especially noteworthy are coastal and highland plant communities. Mangrove belts, of which there are more than 30 varieties, occur where silt is deposited in coastal areas. Upland forests dominated by maples, oaks, and magnolias are found especially on mainland mountain slopes. Human activity has been rapidly altering the stands of virgin forest in Southeast Asia. Most deforestation results from removal for fuelwood and clearing for agriculture and grazing. Although only a relatively small portion of the total land area has been permanently cleared for cultivation—e.g., in Java (Indonesia) and western Luzon (the Philippines)—in some areas shifting cultivation has brought about the replacement of virgin forest with secondary growth. In addition, nearly all countries have commercial logging industries; notable are those in Indonesia, Malaysia, Thailand, and Myanmar. A growing problem has been illegal logging. Thus, timber harvesting has come to contribute significantly to deforestation. Programs in social forestry and reforestation have yet to halt the rapid denuding of the landscape. Animal life Southeast Asia is situated where two major divisions of the world’s fauna meet. The region itself constitutes the eastern half of what is called the Oriental, or Indian, zoogeographic region (part of the much larger realm of Megagaea). Bordering along the south and east is the Australian zoogeographic region, and the eastern portion of insular Southeast Asia—Celebes (Sulawesi), the Moluccas, and the Lesser Sunda Islands—constitutes a transition zone between these two faunal regions. a classroom in Brazil More From Britannica education: Southeast Asia Southeast Asia is notable, therefore, for a considerable diversity of wildlife throughout the region. These differences are especially striking between the species of the eastern and western fringes as well as between those of the archipelagic south and the mainland north. The differences stem largely from the isolation, over varying lengths of geologic time, of species following their migration from the Asian continent. In addition, the tropical rain forests in many parts of the region, with their great diversity of vegetation, have made possible the development of complex communities of animals that fill specialized ecological niches. Especially numerous are arboreal and flying creatures. orangutans orangutansOrangutans (Pongo pygmaeus) in Sumatra, Indonesia. The distinction between the two faunal regions is best depicted by their mammal populations. In general, Australia is inhabited largely by marsupials (pouched mammals) and monotremes (egg-laying mammals), while Southeast Asia contains placental mammals and such hybrid species as the bandicoot of eastern Indonesia. Small mammals such as monkeys and shrews are the most numerous, while in many areas the larger mammals have been pushed into more remote areas and national preserves. Bears, gibbons, elephants, deer, civets, and pigs are found in both mainland and insular Southeast Asia, as are diminishing numbers of tigers. The Malayan tapir, a relative of the rhinoceros, is native to the Malay Peninsula and Sumatra, while the tarsier is found in the Philippines and parts of Indonesia. A number of rare endemic species are found in Indonesia and East (insular) Malaysia, including the Sumatran and Javan rhinoceros, the orangutan, the anoa (a dwarf buffalo), the babirusa (a wild swine), and the palm civet. As the pace of development accelerates and populations continue to expand in Southeast Asia, concern has increased regarding the impact of human activity on the region’s environment. A significant portion of Southeast Asia, however, has not changed greatly and remains an unaltered home to wildlife. The nations of the region, with only few exceptions, have become aware of the need to maintain forest cover not only to prevent soil erosion but to preserve the diversity of flora and fauna. Indonesia, for example, has created an extensive system of national parks and preserves for this purpose. Even so, such species as the Javan rhinoceros face extinction, with only a handful of the animals remaining in western Java

Class activity 1: Crop distribution refers to how crops are spread across different regions in Nigeria. Certain crops are found more in one area than the rest because of the environment in which they grow best. Successful adaptation of crops to the climatic and soil conditions of an area is known as Adaptability. Different crops require different climatic and soil conditions for their normal growth and development. THREE ECOLOGICAL REGIONS IN NIGERIA 1. Coastal region 2. Rainforest region 3. Savanna region Coastal region: This region is close to the sea and is marked by mangrove forest. The climate there is humid and receives lots of rainfall. Dominant Crops: Rice, rubber, coconut. States found: Akwa-Ibom, Bayelsa, Cross-Rivers, Delta, Edo, Lagos, Ogun, Ondo and Rivers. RAINFOREST REGION(SOUTH): This region experiences high rainfall throughout the year and lush vegetation. Dominant Crops: Oil palm, banana, plantain, kolanut, cocoa, tubers(cassava and yam). States found: Bayelsa, Cross River, Edo, Ekiti, Ondo, Osun, Rivers, and Taraba. SAVANNAH REGION(NORTH): This region has a dry and wet season with less rainfall than the forest region. It consists of grassland and a few trees. Dominant Crops cereals, legumes, and cotton. These crops adapt to the drier and warmer climate of the savannah and require less water. States found: Enugu, Ekiti, Osun, Oyo, Kwara, Kogi, Benue, Nassarawa, Plateau, and Taraba States

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