Lecture 7: Geologic Time
Key ideas from readings:
- James Hutton’s Uniformitarianism is an important concept.
- Relative( I am older than you) vs. Absolute ( I am 37 and you are 20) age
- Unconformities ( missing pages in the geologic book of time)
- Fossils what are they and how are they useful?
- How old is Earth and how do we know?
Study questions: Investigation Section 9.15
Table 3 Calculations:
G : 3 and 3,000,000,000
D: 1 and 50,000,000
Table 4 Sequence:
Unconformity on granite
L and V
Lecture 8: Geologic Resources
Key ideas from readings:
- Geologic resources include energy resources, metals and non-metallic resources
1. What determines whether something is a mineral deposit or an ore? What processes form
Most rocks are not considered to be mineral deposits, even though they are indeed
composed of minerals. Instead, the term mineral deposit means the rock is especially rich
in some commodity that might be valuable, and such rocks are said to be mineralized. If
a mineral deposit contains enough of a commodity to be mined at a profit, it is an ore
deposit, and the valuable rocks or other materials in that deposit are ore.
Many geologic processes can concentrate minerals or chemical elements, but it takes
special circumstances to form a mineral deposit, especially one rich enough to become
ore. Some ore-forming environments involve hot or deep processes and others involve
low-temperature processes typical of near-surface environments.
Hot/ deep processes:
- Igneous crystallization
- Hydrothermal deposition
- Hydrothermal replacement
- Weathering enrichment
- Formation by weathering
- Mechanical concentration
- Low- temperature precipitation 2. How do we explore for mineral deposits? Why are industrial rocks and minerals so
important to society?
Geologists explore for new mineral deposits by first studying ones they know about – to
become familiar with any diagnostic attributes that would help the geologist recognize a
new deposit. Geologists then use various strategies and tools to find deposits that are
partially exposed on the surface and those that are completely buried.
Much of the search for new mineral deposits occurs in the field. Mineral –exploration
geologists conduct various investigations. They hike across the countryside doing geologic
mapping, conducting structural studies, and collecting samples for chemical analyses.
Mineral exploration takes geologists to many far-off places.
Industrialized rocks and minerals are so important to society because gold, platinum and
diamonds get all the attention, but modern society especially relies on everyday rocks and
minerals, like limestone and gravel. We use these common materials, called industrial
rocks and minerals, to build much of the infrastructure of our civilization, such as
highways, bridges, water pipes, and sewer lines. We also use them to obtain the material
used to build houses and other buildings.
3. What are the various geologic energy sources? Some of the advantages- increases
investment and profits to the country, and disadvantages of each?
- Coal green house gases, lowers local water table, water pollution
- Natural gas Fossil fuels
- Oil oil spills and air pollution
4. What geologic conditions are necessary for the accumulation of oil and natural gas?
Oil pools are valuable underground accumulations of oil. They are found only where three
specific conditions occur together.
1. Source rock:
Such as shale, containing organic matter that is converted to petroleum
2. Reservoir rock:
Usually sandstone or limestone, that is sufficiently porous and permeable to store and
transmit the petroleum,
3. Oil trap:
A set of conditions to hold petroleum in a reservoir rock and prevent its escape by
Natural gas requires the same conditions as oil for accumulation and formation of gas
5. Differentiate between reserves and resources. Can reserves be increased? Can resources
Reserves( bank balance, always rising and falling with time):
They are a small part of resources. They are the discovered deposits that can be
extracted economically and legally under present conditions. That is, they are the
short term supply of a geologic material. When the final price a company can get for its
product increases, more deposits become economical and reserves increase, even without
Estimate of reserves changes all the time.
Resources( future, lifetime income): It is a broad term used for the total amount of a geologic material in all deposits,
discovered and undiscovered. It includes both the deposits that can be
economically extracted under present conditions and those that may be
extracted economically in the future. It is very difficult to estimate resources because
educated guesses must be made about the existence and sizes of deposits yet
undiscovered as well as about what type of deposit might someday be economical to
Resources cannot be increased because once resources have been carefully estimated the
amount should not change from year to year, for an estimate of resources is basically an
estimate of the total future supply.
Lecture 9: Evolution of Life on Earth
Key ideas from the video:
1. What factors contributed to the evolution of humans?
The factors that contributed to the evolution of humans were bipedalism, learning to walk
on two feet to conserve more energy. Bipedalism evolved due to the tectonic changes to
the east rift valley of Africa when drastic climate changes started to occur and humanoids
had to come down from trees and start walking long distances in search for food and a
better climate to live and survive in. The drastic changes in the environment also helped
humanoids develop larger brain capacity for reasonable thinking which enabled for
humanoids to start using tools and other aspects needed for survival.
2. Why did one species of humanoids triumph over the others?
One species of humanoids triumphed over the others because according to the current
situation in which that species of humanoids were living could not survive the sudden and
drastic changes in their environment. Eg) in Africa within the span 3 million years periods
od extreme climate variability occurred 3 times. Survival of the fittest came into play, and
the smarter and fitter humanoids came to survive the longest, which are humans. This
included learning bipedalism conserve energy for longer periods of time when travelling
due to environment changes occurred. The humanoids that could not adapt to the drastic
changes in the environment died off like Lucy’s kind in the documentary.
They were more adaptable the other species failed to adapt.
1. Write a ½ to 1 page discussion about the factors contributing to the evolution of
humans. Use your own words, but cite evidence (with proper in-text and end
references) from the video and the article as well as any other sources you like.
Tectonics made East Africa highly sensitive to climate changes. As a result of the
formation of the Rift Valley, shifts in global climate caused brief periods during which huge
lakes appeared and disappeared in East Africa. These rapid shifts from very wet to very
dry may have been the environmental stress necessary to push our ancestors down a
human path. Climate has been the reason for the evolutionary change of our early African
ancestors over the last 7 million years. The turnover pulse hypothesis and the variability
selection hypothesis stating that the changing climate altering the landscape from
rainforests to grasslands, and thus causing early hominins to climb out of the trees and
start to walk upright across the new savannas can no longer tell the whole story. The
“savanna hypothesis” states that the incredible change in the landscape of East Africa
sometime after 6 million years ago caused the earliest hominins to evolve bipedalism,
Before this time, food was plentiful in the rainforest. After this time, though, the
hypothesis goes that the spread of grasslands broke up the forest and forced adaption. For
an ape, walking upright is an extremely efficient way of covering vast distances between
food sources, which may have been scarce after the vegetation shift. Grasses did not fully
dominate these landscapes until much later, it was concluded that the early presence of
these grasses allowed for experimentation and adaption that may have been a=employed later, when grasslands began to dominate the ecosystem. Appearance of grasslands alone
was probably not enough to cause bipedalism or a major turnover of new hominin species.
Turnover Pulse hypothesis:
One-directional climate change leading to significant evolutionary changes.
Variability Selection Hypothesis:
Climate change on a much more rapid time scale and without consistent pressure in the
same direction. Dramatic and frequent climate changes drove adaptations that enabled
individuals to cope with a wide range of environmental conditions. These frequent climate
changes thus drove hominins to evolve ways to better adapt to a variable environment.
Two methods adopted by different hominin species:
Brain expansions to think and manage environmental stresses, and massive jaws to eat
anything, whatever the condition.
The periodic extreme climate change that can come from orbital forcing, the wobble of
Earth on its axis of rotation and orbit around the sun affects tropical climates as well.
Rapid climate changes played a major role in speciation, causing adaptive responses to
severe shifts in moisture availability and the consequential changes in the ecosystems.
Previously interpreted as climatic in nature may be primarily controlled by tectonic
changes. Tectonic forcing Africa’s most varied topography. Tectonics modulates local
climate, especially in East Africa. The formation of the East African Rift Valley between 10-
5 million years forever changed Africa’s landscape and climate and the course of human
evolution. In less than 5 million years, East Africa went from a relatively flat area with
abundant rainforests to a region of extreme topography. The rift opened, a region of
mountains, plateaus and deep rift valleys formed, creating the cradle of humanity.
The newly formed East Rift shoulder, or mountain range, prevented moist air from the
Indian Ocean from passing over East Africa and significantly dried the other side of the
mountains, The combination of topography and desert shifted vegetation produced a
climate that varies from cloud forest to desert scrub across the rift. Grasses appeared later
than in the rest of the region and the local hydrology was altered by tectonic changes.
Without considering the tectonic changes and the evolution of the East African Rift,
sedimentary records misinterpreted as primarily being forced by global climate change.
The relationship between orbital forcing, the tropics and moisture availability in the East
African Rift Valley may be the potential causes of changes in hominin evolution. Pulsed
Climate Variability hypothesis links the orbital variation and the new topography. Over the
last 3 million years the East African Rift Valley has become more dry due to short episodes