ว.ธณ. 372 ทรพัยากรธรณีและธรณีพบิตัิภยั

การบา้น 1

ภาคเรียนที ่2 ปีการศึกษา 2554 ก าหนดส่ง: 22 พฤศจิกายน 2554

ค าชี้ แจง: ใหเ้ขยีนตอบดว้ยลายมอืของตวัเอง หา้มพมิพม์าส่ง

1. จงอธิบายความหมายของค าว่า “ธรณีวทิยาสิง่แวดลอ้ม” มาพอสงัเขปตามความเขา้ใจของท่าน

2. การศึกษาธรณีวทิยาสิง่แวดลอ้ม เกีย่วขอ้งกบัศึกษาดา้นต่างๆ ท ัง้ 5 หวัขอ้ ไดแ้ก่

2.1. Earth materials

2.2. Natural hazards

2.3. Landuse planning

2.4. Hydrologic processes

2.5. Geologic Processes (Internal & External) ใหอ้ภปิรายความหมายและขอบเขตของการศึกษาท ัง้ 5 หวัขอ้

ขา้งตน้พอสงัเขป

3. อธิบายหลกัการทางธรณีวทิยาสิง่แวดลอ้มท ัง้ 5 หวัขอ้ (3.1-3.5) ว่าหมายถึงอะไร และมคีวามส าคญัอย่างไร พรอ้ม

ยกตวัอย่างประกอบการอธิบายมาพอสงัเขป

3.1. Human population growth

3.2. Sustainability

3.3. Earth as a system

3.4. Hazardous earth processes

3.5. Scientific knowledge and values

4. อธิบายความหมายของ “สมมตุฐิานกายา (Gaia Hypothesis)”

5. Residence Time (T) คอือะไร?

6. ใหเ้ขยีนบรรยายความเห็นของท่านทีม่ต่ีอค ากล่าวต่อไปน้ี

6.1. กระบวนการภายในโลก (Internal Processes) ก่อใหเ้กิดทรพัยากรแร่ธาตแุละพลงังานทีเ่ป็นประโยชนต่์อมนุษย ์

6.2. กระบวนการภายในโลก (Internal Processes) ก่อใหเ้กิดมหนัตภยัต่อมวลมนุษยชาต ิ

7. อธิบาย ทฤษฎเีพลทเทคโทนิกส ์(Plate Tectonics) มาพอสงัเขป ว่าพฒันาขึ้นมาไดอ้ย่างไร มหีลกัฐานอะไรบา้งที่

สนบัสนุนทฤษฎดีงักล่าว และสามารถน าทฤษฎดีงักล่าวมาใชอ้ธิบายปรากฏการณ์อะไรไดบ้า้ง

8. ใหอ่้านกรณีศึกษา (Case Study 1.1) แลว้สรุปประเดน็ส าคญัของบทความ พรอ้มใหค้วามเหน็ว่าเหตใุดจงึเกิดการล่ม

สลาย (collapse) ของชุมชนบนเกาะอีสเตอร ์

9. เหตกุารณ์พบิตัภิยัทางธรณีวทิยา (Geologic Hazards) มอีะไรบา้ง ใหอ้ธิบายแต่ละอย่างมาพอสงัเขป

10. ใหส้บืคน้ขอ้มูลจ านวนประชากรของประเทศไทยต ัง้แต่อดตีถึงปจัจบุนั (ระบทุีม่าของขอ้มูลดว้ย)

10.1. ค านวณหาค่า และ G (จากโมเดล็การเพิม่ของประชากรในเอกสารทีแ่จกให)้ ทีท่ านายจ านวนประชากรไทยดทีีสุ่ด

10.2. ใหท้ านายว่าในปี พ.ศ. ใด จ านวนประชากรจะเพิม่เป็นสองเท่าของจ านวนประชากรเมือ่สิ้นปี พ.ศ. 2553

While exploring the remote reaches of the Pacifi c in 1722, Dutch sailors came upon a place they named Easter Island,

which was very different from all the others they had seen in the region. Here sailors found an island inhabited by approximately 2,000 people who looked very similar to the Polynesians they had encountered throughout the Pacifi c. However, unlike the seafaring Polynesians with their large canoes crafted from solid tree trunks, Easter Islanders came out to greet them in small, leaky crafts made from a patchwork of small planks and timbers. Even more odd was Easter Island itself. Most other islands in this subtropical climate had rich volcanic soils and lush forests teeming with birds. Instead of a rich paradise, the Dutch found a windswept and grass-covered wasteland, completely devoid of large trees and any native animals larger than insects. Equally strange were the more than 200 stone statues (Figure B1.1) lining the coastline and another 700 in various stages of development. Some statues weighed over 80 tons and were somehow transported as much as 6 miles (9.7 km) from a single quarry in which they were carved. Uncompleted statues weighed as much as 270 tons!

Several intriguing questions have been raised in the years since Easter Island was discovered. First, why was this grass-covered wasteland so unlike the surrounding islands where lush forests, abundant birds, and fl owing streams are common? How could a population of only 2,000 manage to transport and erect 200 huge statues, particularly since they had no suitable trees for making heavy timbers and ropes? Moreover, why would people who were living in caves and struggling to survive by raising chickens and growing crops in thin soils expend such great effort erecting stat-utes? Also puzzling was the islander’s oral history, where they told of their ancestors routinely visiting a well-known reef located 260 miles (420 km) away. How could they have made such a journey in leaky canoes barely capable of sailing offshore their own island? Finally, how in the world did these people ever come to colonize Easter Island in the fi rst place?

The answers to these questions didn’t come about until mod-ern times when scientists from various disciplines began collecting data. Here radiocarbon dates from archaeological excavations fi rst showed that human activity began on Easter Island somewhere between 400 and 700 AD; followed by peak statue construction from 1200 to 1500. Moreover, the density of archaeological sites indicated a population of around 7,000 during the peak period—some estimates go as high as 20,000. A serious population crash obviously must have occurred since only 2,000 people were present when the Dutch arrived in 1722. Also quite revealing was the analy-sis of pollen spores that had fallen into wetlands and incorporated into the sediment record. By comparing the pollen grains found in the various sediment layers to known plant species, scientists could determine the abundance of different plants over time. This analysis proved that large palm trees (up to 6 feet in diameter and 80 feet tall) along with numerous species of shorter trees, ferns, and shrubs had blanketed Easter Island for more than 30,000 years prior to the fi rst human inhabitants. These palm trees would have been ideally

CASE STUDY

1.1 Collapse of a Society Living Unsustainably

suited for constructing the large ocean-going canoes and the tim-bers needed to transport and erect statutes. Similar palm trees today are used in other cultures for their edible nuts and sap.

By examining the bones found in old garbage dumps, scientists were able to determine that the islanders’ diet consisted of large native birds and dolphins in addition to palm nuts. The fact that people feasted on dolphins rather than fi sh was explained by the rela-tively deep water and corresponding lack of coral reefs around Easter Island. This forced the people to sail offshore in order to harvest the only sea animal available in any abundance, namely dolphins. For this, of course, they needed large, seaworthy canoes. Easter Island’s exten-sive forest then provided a direct source of food (birds, nuts, and sap) and the large trees allowed them to build canoes for hunting dolphins

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Hanga RoaHanga Roa

MataveriMataveri

Hanga PikoHanga Piko

South PacificOcean

South PacificOcean

Hanga Roa

Mataveri

Hanga Piko

VolcanoRana Kao

South PacificOcean

Track

Easter Island (CHILE)

PERUPERU

ECUADORECUADOR

CHILECHILE

PERU

Lima

Santiago

Lima

Easter Island(CHILE)

ECUADOR

CHILE

Santiago

0 km 321

0 miles 1 2 3

0 km 1000500

0 miles 500 1000

Region capital

Road

Stone statue (moai)

Cerro Tuutapu270 meters

Cerro Terevaka507 meters

Cerro Puhi302 meters

Volcano Puakatike370 meters

and traveling to distant islands. It was this abundance of natural resources that enabled the population to expand and develop into a highly organized society. Clearly, erecting monuments around the entire island, all from a single quarry, must have required the organiza-tion and cooperation of a large number of people.

The obvious question now is why did this complex society col-lapse? Here again the pollen grains and bones provide the answer. By 800 AD the sediment record includes large amounts of charcoal from wood fi res, but far fewer pollen grains from the palm trees. After inhabiting the island for only a few centuries, the people had begun the process of clearing the forest to grow crops and to pro-vide wood for building canoes, fueling fi res, and transporting stat-ues. Shortly after 1400 AD the palm tree fi nally became extinct. During this period of deforestation the analysis of bones in the islanders’ garbage dumps showed that the number of birds in their diet had decreased dramatically. By around 1500 AD the bones of

native birds as well as dolphins were completely lacking. As the forest was being cut, the islanders were inadvertently eliminating birds and palm nuts from their food supply. Dolphins were soon removed from their diet once there were no more large trees for making seaworthy canoes. Deforestation also led to severe soil loss and decreased the ability of rainwater to infi ltrate the soils. This in turn resulted in thinner and dryer soils, reducing crop production and altering the island’s hydrology such that many of its streams stopped fl owing. Not surprisingly the islanders slowly began to experience both water and food shortages.

The islanders obviously tried to develop new food supplies, but unfortunately their only choices came down to raising more chick-ens and eating each other. Soon their highly ordered society began to unravel into smaller groups of rival tribes, forced to resort to cannibalism and warfare as they all competed for the few remaining resources. By the time the Dutch arrived in 1722, the once vibrant society had completely collapsed, leaving a struggling population

that was a mere fraction of its former size. Without the large palm trees for making seaworthy canoes, the islanders had no means of escape. They were stuck.

In the recent book Collapse by Jared Diamond, the author asks the obvious questions regarding the demise of Easter Island’s society: “Why didn’t they look around, realize what they were doing, and stop before it was too late? What were they thinking when they cut down the last palm tree?” Diamond concludes that the islanders didn’t see the problem because of what he refers to as creeping normalcy. As the years slowly passed, genera-tion after generation of islanders saw only small changes in the amount of forest; hence it looked “normal.” Islanders who understood and warned of the dangers of deforestation likely would have been drowned out by those in society whose jobs depended upon harvesting the trees. Diamond argues that by time the last palm tree was cut, the large old-growth trees were a distant memory. The only remaining trees were small and of little economic signifi cance, thus no one would have noticed the last tree being cut.

Many environmentalists share Diamond’s view that what happened on Easter Island is a small-scale exam-ple of what is currently happening on the entire globe. As Earth’s rising population continues to consume key resources such as petroleum, water, and soil at an unsustainable rate, we are putting our global society at risk of collapse. Moreover, the burning of vast amounts of fossil fuels is having the unintended consequence of accelerated global warming, which may in turn threaten the very survival of humans. Similar to Easter Island in the middle of the vast Pacifi c, Earth is a blue speck in the vastness of space whose people have nowhere to go should they overexploit their natural resources. Unlike Easter Islanders, however, we have history from which to learn the mistakes of others. The question is, will enough of us learn the lessons from history before it is too late?

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