Saturday, February 29, 2020
Characteristics Of Major Agro Ecological Zones Environmental Sciences Essay
Characteristics Of Major Agro Ecological Zones Environmental Sciences Essay Africa is a very large continent with extremely wide range of soils (Bationo et al., 2006). The soils range from shallow with meager life-sustaining capacities to deeply weathered profiles that recycle and support large biomass. In many parts of Africa, inappropriate land use, poor management and lack of inputs have led to soil erosion, salinization and loss of vegetation resulting in a decline of agricultural productivity (Bationo et al., 2006). In Africa and particularly Southern Africa, the most limiting factor to agricultural productivity is soil fertility (Ramaru et al., 2000). Soil fertility is defined as a condition of the soil that enables it to provide nutrients in adequate amounts and in proper balance for the growth of specified plants when other growth factors, such as light, water, temperature, and physical, chemical and biological conditions of soil, are favorable (van der Watt and van Rooyen, 1995). Large areas of sub-Saharan African (SSA) soils, in particular, are af fected by various types of degradation, including fertility decline (FAO, 2001). Soil fertility decline is a deterioration of chemical, physical and biological soil properties. The main contributing processes, besides soil erosion, are: decline in organic matter and soil biological activity; degradation of soil structure and loss of other soil physical qualities; reduction in availability of major nutrients (N, P, K) and micro-nutrients; and increase in toxicity, due to acidification or pollution (FAO, 2001). Soils in most of SSA have inherently low fertility and do not receive adequate nutrient replenishment (FAO, 2001). The SSA has the lowest mineral fertilizer consumption, about 10 kg nutrients (N, P2O5, K2O)/ha per year, compared to the world average of 90 kg, 60 kg in the Near East and 130 kg/ha per year in Asia (Stoorvogel and Smaling, 1990). Agricultural growth in sub-Saharan African countries slightly increased over the past three decades, although not in line with the high population growth rate (FAO, 2001). Food production per capita in sub-Saharan Africa (SSA) has declined since the 1970s, in contrast with the increase in Asia and South America (Figure 1.1). Soil productivity in SSA is also constrained by aridity (low rainfall) and acidity (FAO, 2001) (Table 1.1). South Africa has to face high population growth, poverty, accelerated soil degradation and increasing pressure on land (FAO, 1999b) (Table 1.1). Depletion of soil fertility, along with the related problems of weeds, pests, and diseases, is a major biophysical cause of low per capita food production in Africa. This is the result of the breakdown of traditional practices and the low priority given by governments to the rural sector (Sanchez, 1997). The 1996 World Food Summit highlighted sub-Saharan Africa as the remaining region in the world with decreasing food production per capita (Figure 1.1). The worst levels of poverty and malnutrition in the world exist in this region (Sanchez et al., 1997). A team of scientists has identified declining soil fertility as the fundamental agronomic cause for declining food productivity in Africa. A â€Å"Soil Fertility Initiative for Africa†has been created by a group of international organizations including the World Bank, Food and Agriculture Organization (FAO), International Center for Research on Agroforestry (ICRAF), International Fertilizer Development Center (IFDC), International Fertilizer Association (IFA), and International Food Policy Research Institute (IFPRI).
Thursday, February 13, 2020
Marketing research Paper Example | Topics and Well Written Essays - 1250 words
Marketing - Research Paper Example Today, over half of the 500,000 cars that are sold by Hyundai in USA each year are manufactured within the country itself. The company employs over 20,000 US citizens directly and generates indirect jobs for 6,000 more through its vendors. The company has a marked presence in the states of Alabama, Michigan and California, which house our manufacturing facility, engineering facility, proving grounds and design and research center respectively (Hyundai Motors, 2011). Hyundai’s association with USA goes deeper than just selling cars in the country. Since 1998, Hyundai Motor America, along with Hyundai dealers has been striving to help find a cure to childhood cancer by funding the CureSearch National Childhood Cancer Foundation. The company has hitherto raised $13 million for the cause. Marketing Brief Market Hyundai Motor America, being an automobile manufacturer, is obviously engaged in the automobile manufacturing market in USA. The company manufactures vehicles across variou s categories including, but not limited to compacts, family sedans, crossovers as well as premium vehicles. It also positions its products in various segments based on price starting from prices as low as $9,985 and going as high as $58,000. Main Competitors The competitive landscape of Hyundai Motor America comprises five main competitors viz. Ford Motor, General Motors, Honda, Nissan and Toyota. Hyundai Motors currently holds a 5.3% market share in the US market, but is seen to be steadily catching up to its competitors, recording its three best monthly sales volumes in the country after August 2010 as well as its best ever worldwide sales figure in the same year (PR Newswire). It is currently among the top four foreign car manufacturers in the country. However, the company is also threatened by the rapid progress of global rival Suzuki Motors as well as upcoming names such as Tata Motors and Fiat who are looking to gain a strong foothold in the US market after faring well in the Asian and European markets in identical vehicle segments. The Hyundai premium segment model ‘Genesis’ has also been touted as a competitor to luxury cars like the BMW and the Lexus. Main Customers The main customers of Hyundai Motor America comprise the end user of the automobiles manufactured by them. Like any other automobile manufacturer, Hyundai has an established distribution chain in the country to sell its products directly to the buyer. In other words, it is primarily a B2C company and focuses its marketing on the end consumer. All intermediaries in the sale of Hyundai products are either affiliated with or subsidiaries of the company. Core Competencies Hyundai Motor America, as well as its global contemporaries have a competitive advantage over their opponents through their constant innovations in new technology available at affordable costs to their customers. Features synonymous with any Hyundai car include power, handling, safety, comfort, stability, good cu stomer service and economy in their cars. Every car rolled out by Hyundai motors in the US is expected to have adequate powers, safety measures, simple and responsive controls, comfortable interiors and provide good mileage for that segment. These features are the main reason that Hyundai’
Saturday, February 1, 2020
Robert Rauschenbergs work - Windward Essay Example | Topics and Well Written Essays - 250 words
Robert Rauschenbergs work - Windward - Essay Example Robert Rauschenberg gathered the images and their details from various sources whereby he over painted certain parts of the using his hand by an energetic speed so that he allied the gestural painting of expressionism and the aesthetic value in the style (Joseph, et al, 2002). In Windward, some of his photographs of the statue of liberty with the images of houses so as to confront the politics in the nomination of the pope in the Sistine Chapel. Moreover, his composition is mostly dominated with the pictorial of an eagle so as to stand-in a mysterious and the richly allied discourse between the very many contrasted graphics of the worlds which confront any effort at aesthetic categorization. Robert Rauschenberg collective artwork, symbolizes his spirit of extensiveness, encompassing a reflective overview of his most separate periods, including painting, textile collage, sculptural workings prepared from cardboard and scrap iron, as well as a diversity of pictorials transmission and p rinting approaches. Robert Rauschenberg work embodies certain themes as can be found in many artistic works such as novels, short stories, and the novella. For instance, in the case of Scarlet Letter by Mariama Ba has drawn a very vivid picture in explaining the role of religion to determine the fate of women in the society. Similarly, In Windward, some of his photographs of the statue of liberty with the images of houses so as to confront the politics in the nomination of the pope in the Sistine Chapel.
Friday, January 24, 2020
The Lotus And The Nile :: Botany
The Lotus And The Nile The blue lotus (Nymphaea caerulea) belongs to the Nymphaeaceae (Water-Lily) family. The blue lotus has several common names including: Egyptian lotus, blue water lily, and sacred lily of the Nile. It should not be confused with the "blue lily" or Agapanthus africanus, a plant of an entirely different genus (Anonymous, 1999). Be careful also not to confuse it with the Nymphaea lotus, which is the "white lotus". Fossils of this plant have been dated back to the Jurassic period, about 160 million years ago. Amazingly, the fossils suggest that the blue lotus has not changed much. Other records indicate wide dispersal of this flower before the Ice Age (Edwards, 1998). It is important to first explain a few things about the nature of the blue lotus. The blue lotus or water-lily, is a floating aquatic plant that is known for it's colorful and aromatic flowers. The leaves are waxy, leathery and dark green with a reddish-purple color underneath (Edwards, 1998). The genus Nymphaea includes both tropical and hardy (cold-tolerant) species. There are also night-bloomers and day-bloomers. The tropical day- bloomers are the lotus that was used by the Egyptians (Edwards, 1998). The flowers of many species of lotus have the shocking habit of folding their petals and sinking beneath the water's surface during the night and resurfacing the next day to bloom again (Philbrick and Les, 1996). Many ancient cultures found the blue lotus to be of great use and of esteemed status. In Asia and Africa, the blue lotus symbolized immortality in recognition of the plant's ability to survive and resprout after long droughts, and the seed's ability to remain viable for many years (Edwards, 1998). In China it was regarded as a religious symbol, and a symbol of feminine beauty. Similarly in India, it was compared with the human female form, and in their legends they believe that Brahma, their creator of the universe, sprang from a lotus-like blossom (Edwards, 1998). The Japanese saw a representation of purity and the juxtaposition of good and evil, and the Buddhist's have a prayer mentioning the lotus, "Omi! Mani padme hum!" which is interpreted as, "Oh!, the jewel in the lotus flower!" (Edwards, 1998). The Greeks also admired the blue lotus. They associated the flowers with the mythical nymphs and beautiful maidens thought to inhabit the forests and mountains (Edwards, 1998). The people of Ancient Egypt (Kemet), used the blue lotus extensively in their art and in their everyday uses.
Thursday, January 16, 2020
Philosophy of Gender Essay
Some people aspire for successful lives, but I think success is overrated. What I’m trying to do is living my life according to what I think is right. This means learning not only inside the classroom, but also outside. This is because I believe that education inside the classroom is very limited, which is why we should take the initiative to control our education.            So I start my day by having breakfast. I also read the paper while eating. One must still be aware of the current political and social issues; we must never be isolated from society. These are the people’s issues, so we must not be isolated from what they are engaged in. We are working for a better society not for ourselves, but also for other people and the next generation, so we must be integrated with their issues.            After breakfast, I go to school. In school, aside from attending class, I talk to the personnel. I ask their opinion on issues. I ask how their lives are. Through this way, I get a perspective on how they think. It is very interesting because they are usually very outspoken. Sometimes, I learn so much more from them than the textbooks they make us read in class.            After class, I sometimes do volunteer work. I treat this as my â€Å"other class.†It supplements what I learn in class, and sometimes I get to apply what I learned inside the classroom as well. This class teaches me a lot, from relating with other people to critical thinking. Then I go home. I eat, study, then read. I may not have a lot of stuff, but I do have a lot of books. I love reading. This opens my mind to a lot of possibilities, as well as solutions. I also love reading about great odds being surpassed by ordinary people.            For a democracy to work, I think the citizens should be proactive people. For this to happen, they have to be trained even while in school. And this would entail letting them take control of their education, planning their own curriculum, carrying out their own lesson plan. When one speaks of a rational state of consciousness, one is talking of the state when one’s mind is consciously doing something, like crossing the street. This kind of state requires one’s full attention. When one speaks of non-rational consciousness, it is when one’s mind is engaging in an activity that one’s mind can do subconsciously; its whole attention is not on the activity. Habits and learned behavior fall under this state. An example would be tapping one’s foot. And when one talks of the irrational state, it is the state of being unconscious, such as sleeping deeply. When in this state, one is unaware of what is happening. Have you had your heart broken? I have, once. I loved her, but she left me. Maybe she thought the world is a better companion. I do not know. It has been years.            Her name was Lilith. She was a remarkable being, all magic and desire. She had hair that was like waterfalls cascading down to earth; fluid, wild, breath-taking, hypnotizing. Her body was like the hills and mountains of the earth, curvaceous and fertile. She also provided the intellectual stimulation that I needed. In my youth, I was too arrogant and stubborn to see that.            I had asked Father for a mate. I was lonely, and I had no one to share my experiences of naming and taking care of the creatures Father put under my care. I also wanted someone who would complement my efforts of organizing the whole of Creation, listening intently, while serving me a delicious meal. So I told the Father how lonely I was.            He made a mate, and called it woman. I accepted her, and we lived together. I thought we were going to be happy together forever in paradise. I made her wait on me, serve me, obey me. I wanted her to only wander when I was with her. I wanted her to do all the domestic duties, because I was busy managing the Garden of Eden.            We got along sometimes. Lilith, skilled with words, would contribute to my summary of what I did during the day, pointing out which names fitted the creature exactly. I thankfully used her suggestions, being inept with words, having been alone for some time. But mostly we fought day and night. We had different views on most things. She wanted to talk about how we feel; I could not successfully keep up with her analysis on why she is annoyed when the sheep just leaves its droppings lying around. She wanted to do things on her own; she could not understand that I was afraid of losing her, which is why I do not want her wandering off. She wanted the privilege of naming and managing the creatures in Creation; I could not make her understand that this was a job given to me, and she should try other activities in the Garden. She talked of how Eden could be made better; I would rather focus on the conditions now.            So we fought. She would not do the things I told her were her duties as my wife. She said she wanted to do other things. She could not understand that her declining means undermining my authority. I know I should not have shouted at her and pulled her hair, but she made me angry. So when she left, I did not go looking for her. We have had disputes before, and though it is unlike her to not talk the problem over, I decided to pay no heed.            But then, days after, she has not yet returned. So I told the Father of my concern. He sent messengers to her, but she would not yield. She would not come back to Eden, to me.
Tuesday, January 7, 2020
Opinion on Abortion Essay - 1156 Words
Opinion on Abortion Abortion is when a foetus is expelled from its mothers womb before the pregnancy reaches full term (usually 40 weeks). The abortion act says that a woman can have an abortion if the pregnancy would put her in danger, or if the baby was so handicapped that it could not survive independently and it would have no quality of life. The act also says that these reasons for abortion are accepted whereas a woman who simply did not want another child would not be allowed to abort her pregnancy. Many Christians oppose abortion. Two reasons that they give for this are because they believe that life begins at conception and so to abort an embryo would be considered as murder. They†¦show more content†¦Some passages of the Bible also teach that God has planned each being and planted them in the womb: For you created my inmost being; you knit me together In my mothers womb. This backs up the Christians point of view giving a strong argument for abortion and reasons using references from the Bible and what God seemingly wanted. Some churches would believe abortion to be allowed because there are some situations where the most loving thing to do would be to abort the pregnancy. One situation would be where the mother is endangered by the pregnancy and a possible effect of this would be the death of both the mother and the child. The most loving thing to do in the situation would be to save the mother by aborting the foetus. The United Reformed church believes that there is a difference between an undeveloped embryo and a foetus about to be born. They would not think of a few-week-old embryo as a child. They believe that sometimes abortion is necessary but that it should be taken seriously. Another possible scenario would be mother pregnant with the child of a rapist. This is a tough question, but would you keep the baby or not? The Church of England would allow an abortion because of the trauma involved with raising the child and the father.Show MoreRelatedA Opinion On Abortion And Abortion897 Words  |  4 PagesEveryone has a different opinion on abortion. According to the Merriam- Webster dictionary, an abortion is â€Å"the termination of a pregnancy after, accompanied by, resulting in, or closely followed by the death of the embryo or fetus, spontaneous expulsion of a human fetus during the first 12 weeks of gestation, induced expulsion of a human fetus, expulsion of a fetus by a domestic animal often due to infection at any time before completion of pregnancy.†Abortion is, and always will be a controversialRead MoreEssay on Opinion on Abortion1141 Words  | 5 PagesOpinion on Abortion My own opinion of abortion is very varied. There are so many different reasons for abortions. Every woman who has had one will have had reasons. I am sure they wouldnt have decided in a few minutes that they were going to abort their baby. They would have thought long and hard about what to do. I put myself in the position of someone else. If I got pregnant now would I really be able to keep it. I would, for one, have to stop school and miss outRead MorePolitical Opinions on Abortion Essays1223 Words  | 5 PagesAbortion is one of the most hotly contested social issue’s in American politics. It has been used as a political tool by the Republicans (conservative Right) to mobilize its opponents as a strong voting block within the party. On the other side, the Democrats (liberal Left) has use their pro-choice stance over the issue to mobilize women voters, along with other proponents who believe that abortion should be a viable option for pregnant women. It is in this context in which the political debate ofRead MoreA Literature Review of the Popular Opinion on Abortion1651 Words  | 7 Pagesï » ¿Literature Review Popular Opinion on Abortion Abortion has long been a source of acrimonious and controversial debate. It touches upon key ethical, moral, philosophical, biological, and legal issues. Opinions about abortion tend to be rooted in fundamental personal values which are unlikely to change. Many people, especially Christians, regard abortion as murder. Such people oppose abortion in varying degrees, calling their position Pro-Life. Others regard abortion as an excruciating yet criticalRead MoreReligious Opinions and Views on Abortion Essay1407 Words  | 6 PagesReligious Opinions and Views on Abortion In examining religious opinions on abortion, one must find common ground on which to form a foundation of comparison. With most of the religions to date, that common ground lies on the argument of whether or not a fetus is an actual person. Some religions protest by saying a fetus isnt a conscious being -- therefore there is no loss in doing away with it. But for those religions that do believe there is a life -- or any spiritual being -- in a fetusRead MoreAbortion Is Wrong: An Opinion Essay2433 Words  | 10 PagesAbortion is Wrong The argument should abortion be legal or illegal? can be argued both ways, and where I stand is somewhere in the middle. I am Catholic, and believe strongly that abortion is a sin because it constitutes the murder of human life. However, I also believe that abortion should be allowed for women who were raped. An accidental pregnancy, however, is not an excuse to have an abortion. The practice of carrying the child to term sometimes wakes up the woman to the possibility of motherhoodRead MoreSocietal Attitudes Toward Abortion : Public Opinion Varies Based On The Situation Surrounding The Pregnancy1606 Words  | 7 PagesSocietal Attitudes Toward Abortion Public opinion varies based on the situation surrounding the pregnancy. Whether it may be an unplanned pregnancy or a rape, the topic of abortion always receives different extremities of reactions. In situations where a privileged couple gets pregnant and simply does not have time for a baby and gets an abortion, the public may react differently than from a situation where a 15 year old girl is raped by her stepfather and gets pregnant. There appears to be a spectrumRead MoreArgumentative Essay On Abortion1546 Words  | 7 Pagesmother.†Abortion is the way of ending pregnancy by removing the fetus or embryo before it can survive outside the matrix, which can also allow women to choose whether they want to become a mother or not. However, people have developed the controversy about abortions. Abortion debate is an ongoing debate which has involved moral, legal, biological and religious status of the induced abortion. In this controversy, there are two groups emerged. The gro up of people who hold the opinion that abortion shouldRead MoreAmerican History: Fighting for the Freedom of Choice763 Words  | 3 PagesAbortions being made illegal in the late 1880’s created a lot of â€Å"underground†abortion procedures. The abortions performed were not safe, they were expensive, and often time’s male doctors would force women to have intimate relations with them before the procedure. In the 1950s, about a million illegal abortions a year were performed in the U.S., and over a thousand of those women died each year as a result. It wasn’t until the civil rights and antiwar movements in the 1960’s that women began toRead More Abortion Essay1082 Words  | 5 Pages ABORTION Abortion, in my opinion, has been one of the largest debataable issues in American Society. There are so many aspects and views to examine before one can even begin to form their own opinion. In order to discuss an important issue such as abortion, we must first understand what it means. Abortion is the ending of a pregnancy before the fetus has developed and grown enough to live outside the mother. When abortion happens naturally before the 20th week it is called a spontaneous abortion
Monday, December 30, 2019
The Earths Crust Everything You Need to Know
The Earths crust is an extremely thin layer of rock that makes up the outermost solid shell of our planet. In relative terms, its thickness is like that of the skin of an apple. It amounts to less than half of 1 percent of the planets total mass but plays a vital role in most of Earths natural cycles. The crust can be thicker than 80 kilometers in some spots and less than one kilometer thick in others. Underneath it lies the mantle, a layer of silicate rock approximately 2700 kilometers thick. The mantle accounts for the bulk of the Earth. The crust is composed of many different types of rocks that fall into three main categories: igneous, metamorphic and sedimentary. However, most of those rocks originated as either granite or basalt. The mantle beneath is made of peridotite. Bridgmanite, the most common mineral on Earth, is found in the deep mantle. How We Know the Earth Has a Crust We didnt know the Earth had a crust until the early 1900s. Up until then, all we knew was that our planet wobbles in relation to the sky as if it had a large, dense core -- at least, astronomical observations told us so. Then along came seismology, which brought us a new type of evidence from below: seismic velocity. Records of seismic waves allow seismologists to locate and measure the size of events like these, and to map the Earths internal structure. jamesbenet/Getty Images Seismic velocity measures the speed at which earthquake waves propagate through the different materials (i.e. rocks) below the surface. With a few important exceptions, seismic velocity within the Earth tends to increase with depth. In 1909, a paper by the seismologist Andrija Mohorovicic established a sudden change in seismic velocity -- a discontinuity of some sort -- about 50 kilometers deep in the Earth. Seismic waves bounce off it (reflect) and bend (refract) as they go through it, the same way that light behaves at the discontinuity between water and air. That discontinuity named the Mohorovicic discontinuity or Moho is the accepted boundary between the crust and mantle. Crusts and Plates The crust and tectonic plates are not the same. Plates are thicker than the crust and consist of the crust plus the shallow mantle just beneath it. This stiff and brittle two-layered combination is called the ​lithosphere (stony layer in scientific Latin). The lithospheric plates lie on a layer of softer, more plastic mantle rock called the asthenosphere (weak layer). The asthenosphere allows the plates to move slowly over it like a raft in thick mud. We know that the Earths outer layer is made of two grand categories of rocks: basaltic and granitic. Basaltic rocks underlie the seafloors and granitic rocks make up the continents. We know that the seismic velocities of these rock types, as measured in the lab, match those seen in the crust down as far as the Moho. Therefore were confident that the Moho marks a real change in rock chemistry. The Moho isnt a perfect boundary because some crustal rocks and mantle rocks can masquerade as the other. However, everyone who talks about the crust, whether in seismological or petrological terms, fortunately, means the same thing. In general, then, there are two kinds of crust: oceanic crust (basaltic) and continental crust (granitic). Oceanic Crust An illustration of oceanic crust. Dorling Kindersley/Getty Images Oceanic crust covers about 60 percent of the Earths surface. Oceanic crust is thin and young -- no more than about 20 km thick and no older than about 180 million years. Everything older has been pulled underneath the continents by subduction. Oceanic crust is born at the mid-ocean ridges, where plates are pulled apart. As that happens, the pressure upon the underlying mantle is released and the peridotite there responds by starting to melt. The fraction that melts becomes basaltic lava, which rises and erupts while the remaining peridotite becomes depleted. The mid-ocean ridges migrate over the Earth like Roombas, extracting this basaltic component from the peridotite of the mantle as they go. This works like a chemical refining process. Basaltic rocks contain more silicon and aluminum than the peridotite left behind, which has more iron and magnesium. Basaltic rocks are also less dense. In terms of minerals, basalt has more feldspar and amphibole, less olivine and pyroxene, than peridotite. In geologists shorthand, oceanic crust is mafic while oceanic mantle is ultramafic. Oceanic crust, being so thin, is a very small fraction of the Earth -- about 0.1 percent -- but its life cycle serves to separate the contents of the upper mantle into a heavy residue and a lighter set of basaltic rocks. It also extracts the so-called incompatible elements, which dont fit into mantle minerals and move into the liquid melt. These, in turn, move into the continental crust as plate tectonics proceeds. Meanwhile, the oceanic crust reacts with seawater and carries some of it down into the mantle. Continental Crust Continental crust is thick and old -- on average about 50 km thick and about 2 billion years old -- and it covers about 40 percent of the planet. Whereas almost all of the oceanic crust is underwater, most of the continental crust is exposed to the air. The continents slowly grow over geologic time as oceanic crust and seafloor sediments are pulled beneath them by subduction. The descending basalts have the water and incompatible elements squeezed out of them, and this material rises to trigger more melting in the so-called subduction factory. The continental crust is made of granitic rocks, which have even more silicon and aluminum than the basaltic oceanic crust. They also have more oxygen thanks to the atmosphere. Granitic rocks are even less dense than basalt. In terms of minerals, granite has even more feldspar and less amphibole than basalt and almost no pyroxene or olivine. It also has abundant quartz. In geologists shorthand, continental crust is felsic. Continental crust makes up less than 0.4 percent of the Earth, but it represents the product of a double refining process, first at mid-ocean ridges and second at subduction zones. The total amount of continental crust is slowly growing. The incompatible elements that end up in the continents are important because they include the major radioactive elements uranium, thorium, and potassium. These create heat, which makes the continental crust act like an electric blanket on top of the mantle. The heat also softens thick places in the crust, like the Tibetan Plateau, and makes them spread sideways. Continental crust is too buoyant to return to the mantle. Thats why it is, on average, so old. When continents collide, the crust can thicken to almost 100 km, but that is temporary because it soon spreads out again. The relatively thin skin of limestones and other sedimentary rocks tend to stay on the continents, or in the ocean, rather than return to the mantle. Even the sand and clay that is washed off into the sea returns to the continents on the conveyor belt of the oceanic crust. Continents are truly permanent, self-sustaining features of the Earths surface. What the Crust Means The crust is a thin but important zone where dry, hot rock from the deep Earth reacts with the water and oxygen of the surface, making new kinds of minerals and rocks. Its also where plate-tectonic activity mixes and scrambles these new rocks and injects them with chemically active fluids. Finally, the crust is the home of life, which exerts strong effects on rock chemistry and has its own systems of mineral recycling. All of the interesting and valuable variety in geology, from metal ores to thick beds of clay and stone, finds its home in the crust and nowhere else. It should be noted that the Earth isnt the only planetary body with a crust. Venus, Mercury, Mars and the Earths Moon have one as well. Edited by Brooks Mitchell
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