King David Comprehensive College

Penn Emile Nkeng

CLASS: LOWER SIXTH SCIENCE

SUBJECT: GEOLOGY

TOPIC: IGNEOUS PETROLOGY AND PALEAONTOLOGY

OBJECTIVEs: At the end students should be able to use textures in order to determined environment of formation of igneous rocks. Paleontologically should know the various methods of preservation of fossils, types of fossils and important of fossils to geologist.

IGNEOUS TEXTURES

Igneous Rock Textures Texture refers to a rock’s appearance with respect to the size, shape, and arrangement of its grains or other constituents.  Most (but not all) igneous rocks are crystalline; that is, they are made of interlocking crystals (of, for instance, quartz and feldspar). The most significant aspect of texture in igneous rocks is grain (or crystal) size.

Extrusive rocks typically are fine-grained rocks, in which most of the grains are smaller than 1 millimeter. The grains, if they are crystals, are small because magma cools rapidly at the Earth’s surface, and so they have less time to form.

 Intrusive rocks are also fine-grained; these occur as smaller bodies that apparently solidified near the surface upon intrusion into relatively cold country rock (probably within a couple kilometers of the Earth’s surface ). Basalt, andesite, and rhyolite are the common fine-grained igneous rocks. Igneous rocks that formed at considerable depth—usually more than several k ilometers—are called plutonic rocks (after Pluto, the Roman god of the underworld).

 Characteristically, these rocks are coarse-grained, reflecting the slow cooling and solidification of magma 1 millimeter and cannot be distinguished by the unaided eye. So, for practical purposes, if you can discern the individual grains, regard the rock as coarse-grained; if not, consider it fine-grained. Some rocks are porphyritic; that is, large crystals are enclosed in a groundmass of finer-grained crystals or glass.

Porphyritic extrusive rocks are usually interpreted as having begun crystallizing slowly underground followed by eruption and rapid solidification of the remaining magma at the Earth’s surface. Some porphyritic rocks have a coarse-grained groundmass in which the individual grains are over 1 millimeter. The larger crystals enclosed in the groundmass are much bigger, usually two or more centimeters across. Porphyritic granite is an example.

Identification of Igneous Rocks Igneous rock names are based on texture (notably grain size) and mineralogical composition (which reflects chemical composition). Mineralogically (and chemically) equivalent rocks are granite-rhyolite, diorite-andesite, and gabbro-basalt.  

PALEONTOLOGY

It is the scientific study of pre-historic life (animals and plants) whose remains and other indications are preserved in sedimentary rocks. It includes the study of fossils to determine their evolution and their interaction with each other and their environment. This branch of geology is important in stratigraphy for the purpose of determining past environments (paleoenvironmental analysis), correlation, strata identification and the establishment of sequences.

Fossil refers to the preserved remains of dead organisms. This includes extinct organisms and those with living species. Only remains older than 10,000 yrs were considered fossils. This limitation has been abandoned and any ancient remain of living organism can be considered fossils regardless of its age.

Since the creation of the earth many species of organisms have existed but not all have been preserved. Some fossils have not preserved because of the following:

1. Bacteria action is capable of completely destroying dead organisms especially those without hard parts.
2. Metamorphism which is controlled by increasing temperature, pressure and stress, tends to completely destroy already preserved remains or fossils.
3.  Percolating solutions especially acid solutions promote the dissolution of fossils.
4. Igneous activities also help destroy preserved fossils in rocks.
5. Constant mechanical weathering especially in high current environments also destroys fossils.

CONDITIONS FOR FOSSILIZATION

1. Presence of Hard parts: The organism must have hard parts. This is fulfilled by vertebrates and invertebrates because they are made up of skeletons, bones, teeth and shells and skeletons respectively. Examples include:

• Insects having chitinous materials, a fibrous polysaccharide which is difficult to decay.
• Musluscans with calcareous shells.
• Graptolites with hard scleroprotein shell.
• Plants made up of cellulose materials.

1. Rapid Burial: The remains of the organism should be rapidly buried. This is to prevent decay and destruction of the remains. Thus the marine environment (continental shelf and slope) is highly favorable for fossilization because of high rate of deposition.
2. Abundance of Organisms: The larger the population of organisms in an environment the higher the probability of preservation.
3. Age: Older or advanced forms of organisms have well developed morphological features which will be more durable and will be preserved for longer periods of time.
4. Size of the Organism: Small sized organisms are easily preserved because they are easily buried thus they are common as fossils than large organisms which take longer time to be buried.

Potential of Environments for Fossilization

Two major environments are considered: continental and marine environments.

In the continental environments, accumulation of sediments is not rapid owing to the unstable nature of this environment. Denudation processes constantly destroys rocks and reworks already formed sediments preventing the burial of remains of organisms. In addition, organisms in this environment are commonly large in size reducing their rate of burial.

In the marine environment, the littoral region is very unstable with constant wave activities thus preventing the burial and preservation of fossils. The continental shelf which occurs at 0 – 200m depth is favorable for fossilization. It comprises the photic zone which is a thriving environment for zooplankton and phytoplankton. Thus with the huge population of organisms and rapid deposition of sediments, fossil are greatly preserved in this environment. Furthermore the continental slope and which is a very stable environment, composed of fine grained rocks is a favorable environment for fossilization.

MODES OF PRESERVATION

1. Preservation of the Entire Organism: This is a rare occurrence because the soft tissues of organisms are easily attacked and destroyed by bacteria. Examples of this case include: insects preserved in amber/resin and wooly mammoth frozen in ice in Siberia.
2. Preservation of Skeletons unchanged: This is the preservation of hard parts (skeleton) unaltered after the decay of soft tissues. These hard parts include shells, teeth, bones etc.
3. Preservation of Hard Parts after Alteration: Hard parts of organisms are altered in the following ways before preservation:

1. Conversion of Aragonite and Calcite: some shells of organisms are made up of aragonite. This is common in young organisms. The aragonite is usually converted to a stable form Calcite through recrystallization. Thus aragonite shells can be encountered in recent sediments while calcite rich shells are common in older rocks.
2. Petrifaction: Also known as permineralization, it takes place through two ways

1. Impregnation: This is the deposition or infilling of mineral matter into bones and shells by ground water. The bones and shell differ in composition and become denser and harder thus easily preserved. Fine structures are destroyed during this process.
2. Replacement: in this case one mineral or minerals substitute for other minerals in the buried remains. This can take place by coarse replacement which preserve fine structures and fine or molecular replacement.

The resulting fossil has different chemical composition from the original one. Common petrifying minerals are: silica, calcite, limonite, macasite, haematite and pyrite.

1. Hard parts preserved after Partial Alteration:

• Carbonization of Some components: This involves the reduction of some soft tissues by solutions and some chemicals into thin films of carbon. Fine structures are usually preserved. Through this process other organic components are preserved e.g. chitin, scleroprotein, cellulose and lignin.
• Mummification: It is the natural dehydration of soft and hard parts of organisms in hot and dry climate such as in the arid environments e.g. extinct type of sloths are seen preserved in Mexico
• Preservation in Peat and Tar: This is made possible by the antiseptic property of these materials. Some bones of Pleistocene giant deers have been found preserved in these deposits and also in tar pools in the U.S.A.

1. Complete Loose of Hard Parts: This involves the complete destruction of hard parts by percolating acid solutions. The impressions of these parts are left imprinted in sediments or rocks as moulds and casts.

Moulds are impressions of the hard parts of organisms preserved in surrounding sediments once the hard tissues are destroyed. If the external features are preserved, it is described as external mould. If the internal features are preserved, it is described as internal mould.

Casts  on the other hand refers to impressions left behind when minerals or sediments fill mould cavities or the cavities left after these parts are destroyed leaving behind impressions on these minerals or sediments. These include internal and external casts.

1. Trace Fossils or Ichnofossils: These represent evidences of organic life and include burrows, trails, tracks and other evidences of organic life. They are commonly preserved in fine grained sedimentary rocks such as shale, clay and mudstone.

TYPES OF FOSSILS

 Transported Fossils

A layer of sedimentary rock may contain fossils of organisms preserve in place. Such fossils are typically benthonic fossils. Most sedimentary rock layers contain fossils of organisms from different environments such as land plants and animals preserved in marine rocks. Evidences of transportation are broken shells, worn and sorted shells, alignment of shells and the dislocation of valves and oscicles.

Derived Fossils

Fossils preserved in place could be found in association with fossils from earlier formations. Derived fossils are fossils that have been fossilized formations, eroded from its original site and incorporated in another younger geological formation. They are also known as reworked or remanié fossils.

Uses of Fossils

1. Fossils are used to divide chronological divisions within the geologic time scale i.e. used to distinguish major stratigraphic units. A sequence of strata can be divided into zones or small sections based on the characteristic occurrence of a particular assemblage or association of fossils. Such fossils are known as zone fossils or index fossils based on the scale of the zone or section they characterize. Zone fossils or index fossils must fulfill the following conditions:

• Must be abundant
• Must be easily distinguished
• Must have a short life range (short ranging)
• Must have a wide geographical range
• Must be well developed.

1. Fossils are used for relative dating and for correlation. Strata can be identified and matched with others (correlation) by means of their zonal assemblages.
2. Fossils are use for past environmental analysis or reconstruction. Some fossils embedded within sedimentary rocks, indicate particular environments. For example:

• The presence of gastropods and bivalves indicate fresh water or brackish water environments.
• Brachiopods, corals and cephalopods indicate marine environment.
• Reef corals indicate clear warm shallow marine environment.
• Frozen mammals indicate periods of prolonged glaciations.

1. Fossils such as foraminifera and pollen grains indicate fossil fuel.
2. They also provide the most useful evidence of evolution.

ASSIGNMENT. Using the description, pick any rock around your home and give its tex

LESSON NO 5

Reading comprehension (10MRKS

Read the following passage and answer the questions that follow it.  Circle  the letter A, B, C or D that corresponds to the most appropriate answer.

       Extend rights and opportunities to more o your citizens. See the differences and diversity in this country as strength, just like we in America see our diversity as strength and not a weakness. So, you can choose the path to progress; but it requires making some important choices.

       First, it means continuing down the path of a strong more inclusive, more accountable and transparent democracy. Democracy begins with a peacefully elected government. It begins with elections but it doesn’t stop with elections. So, your constitution offers a roadmap to governance that’s more responsive to the people through protection against unchecked power, and more power in the hands of local communities. For this system to succeed, there also has the be space for citizens to exercise their rights and we saw the strength of Kenya’s Civil Society in the last election when groups collected reports of incitement so that violence could be stopped before it span out of control..

      The ability for citizens to organize advocate for change, that is the oxygen upon which democracy depends. Democracy is sometimes messy and for some of us, leaders, sometimes it’s frustrating. Democracy means that someone is always complaining about something. Nobody is ever happy in a democracy about their government. If you make one person happy, somebody else is not happy and sometimes, somebody you made happy, later on they  are not. They say, “ what have you done for me lately? “

But that’s the nature of democracy – that’s why it works, because it’s constantly challenging leaders to up their game and to do better and such civic participation and freedom is also essential for rooting out the cancer of corruption.

        I want to be clear, corruption is not unique to Kenya. There is no country that is completely free of corruption. Certainly, here in the African continent, there are many countries that deal with this problem and I want to assure you, I speak about it wherever I go, not just here in Kenya. But the fact is too often, here in Kenya as is true of other places: corruption is tolerated because that’s how things have always been done. People just think that that is the normal state of affairs, and there was a time in the United States when that was true too – my own town of Chicago was infamous for Alcapone and the Mob and organized crime corrupting law enforcement. But what happened was over time, people got fed up and leaders stood up said, ‘we are not going to play that game anymore.’ And you change the culture and habits.

          Here, in Kenya, it is time to change habits and decisively break that cycle because corruption holds backs every aspect of economic and civil life. It’s an anchor that weighs you down and prevents you from achieving what you could.  If you need to pay bribe and hire somebody’s brother who is not very good and doesn’t come to work in order to start a business, then that is going to create less jobs for everybody. If electricity is going to limit development of the country as a whole.

     It is important that not only low level corruption that not only low level corruption is punished but also folks at the top. If they are taking from the people, then that has to be addresses as well. But it’s not something that is just is fixed by laws or any one person can fix. It requires a commitment by the entire nation – leaders and citizens to change habits and to change culture. Tough laws need to be on the books, and the good news is that your government is taking some important steps in the right direction. People who break the law and violate the public trust spotlight trust need to be prosecuted, NGOs have to be allowed to operate to shine a spotlight on what needs to change, and ordinary people have to stand up and say, ‘enough is enough’. It’s time for a better future. As you take these steps, I promise that America will continue being a partner in supporting investments and strong democratic institutions.   

Elements for development that extends economic opportunity and dignity for all of Kenya’s people. America partners with Kenya in areas where you are making enormous progress. We focus on what Kenyans can do for themselves in building capacity, on entrepreneurship where Kenya is becoming an engine for innovation, on access to power where Kenya is developing clean energy that can reach more people; on the important issue of climate change where Kenya’s recent goal to reduce its emissions has put it in the position if being a leader on the continent; on food security where Kenya’s crops are producing more to meet the demands of your people and a global market, and on health where Kenya’s struck huge blows on HIV/AIDS and other diseases while building up the capacity to provide better care for local communities.

     America is also partnering with you on an issue that’s fundamental to Kenya’s future. We are investing in youth.  We are investing in the young people of Kenya and the young people of this continent. Robert F. Kennedy once said, ‘it is a revolutionary world that we live in and it is the young people who must take the lead.’ So through our Young African Leaders Initiative, we are empowering and connecting young people from across the continent who are filled with energy and optimism and idealism and are going to take Africa to new heights; and these young people are not weighed down by the old ways. They are creating a new path.   These are the elements for success in this 21st century.

     To continue down this path of progress, it will be vital for Kenya to recognize that  no country can achieve its full potential unless it draws on the talents of all its people and that must include the half, who are women and girls…Every country and every culture has traditions that are unique and help make that country what it is.

But just because something is a part of your past doesn’t make it right. It doesn’t mean that it defines your future. Now, look at us in the United States, recently we’ve been having a debate about the confederate flag. Some of you may be familiar with this. This was symbol  for those states who fought against the Union to preserve slavery. As a historical artifact, it’s important; but some have argued that it’s just a symbol of heritage that should fly in public spaces. The fact is (that) it was a flag that flew over an army that fought to maintain a system of slavery and racial subjugation. So, we should understand our history but we should also recognize that it it sends a bad message to those who were liberated from slavery and oppression, in part because of (an) unspeakable tragedy that took place recently, where a young man who was a fan of the confederate flag and, racial superiority shot helpless people in a church. More and more Americans of all races are realizing now that that flag should come down.

Just   because something is tradition doesn’t make it right. Around the world, there is a tradition of repressing women and treating them differently-not giving them the same opportunities, and husbands beating their wives and children not being sent to school. Those are bad traditions – treating women and girls as second class citizens. Those are bad traditions; they need to change. They are holding you back. Treating women as second class citizens is a bad tradition, it holds you back. There is no excuse for sexual assault or domestic violence. There is no reason that young girls should suffer genital mutilation. There is no place, in civilised society, for early or forced marriage of young girls. These traditions may date back in centuries: they have no place in the 21st century. These are issues of right and wrong in any culture; but they are also issues of success and failure. Any nation that fails to educate its girls or employ its women and allows them to maximize their potential, is doomed to fall behind in the global economy.

Evidence shows that communities that give their daughters the same opportunities as their sons are more peaceful, prosperous; they develop faster, and are more likely to succeed. That’s true in America; that’s true here in Kenya, it doesn’t matter…

       There are real threats out here … we are grateful for the sacrifices made by Kenyans on the frontline …We are going to stand shoulder to shoulder  with you in this fight against terrorism for as long as it takes. But as I mentioned yesterday, it is important to remember that violent extremists want us to turn against one another. That’s what terrorists typically try to exploit. They know that they are a small minority. They know that they can’t win conventionally. So, what they try to do is target societies where they can exploit divisions. That’s what happens in Irap; that’s what happens around the world…Extremist who prey on distrust must be defeated by communities who stand together and stand for something different …we have to rejects calls that allow us to be divided…Kenya is stronger when Kenyans stand united with a sense of national identity… I love Kenya because you feel at home any where you go. Home anywhere you go. That’s the Kenya that welcomed me almost 30 years ago as a young man. You helped to make me feel at home and standing here today as president of the United States while I think about all those young people and the young people in the attendance here. You will make me feel at home and I’m confident that your future is going to be written across this country and across this continent by young people like you.

Young men and women, we don’t have to struggle under colonial power. We don’t have to look overseas to realize your dreams. Yes, you can realize your dreams. Yes, you can realise your dreams right here right now. We have not inherited this land from our forebears; we have borrowed it from our children. So, now is the time for us to do the hard work of leaving up to that inheritance of building a Kenya where the inherent dignity of every person is respected and protected, and there is no limit to what a child can achieve and I’m here to tell you that the United States of America will be a partner for you every step on the way. 

An excerpt of  President Obama’s speech to the people of Kenya on his visit to that  country, In 2015.

Questions:

1)            According to the …………………………is a universal socio-political malaise.

(A)          Poverty   (B)Democracy    (C)Corruption   (D)Religion

2)The writer in this passage sounds………………………………………

(A)Prescriptive      (B)Descriptive      (C) Complacent    (D)Satisfied

3) The path to progress in the passage consists of…………………………………………….

(A)inclusive  democracy, development that extends economic opportunity and dignity for all and choosing a future of peace and reconciliation.

(B)educating girls and employing women

(C) fighting corr