Unit 8

Unit 8 Review WS

1. Describe the difference between weather and climate.

Weather is the temperature, precipitation, wind, and humidity conditions in a small area over hours/days/weeks; while climate is the atmospheric weather conditions in a large area over years/decades/centuries. 

Climate is what we expect (cold weather in January in Minnesota) Weather is what we get (-20° in March on a random Tuesday). 

2. Describe how each of the following influence local climate:

• Latitude

High latitudes contain less heat energy because solar radiation is dispersed over a large area. Therefore, it is less intense. 

• Topography

Topography influences local climate through rain shadows, katana tic winds, and table mountain cloud flow. All of these factors influence local climate through temperature, physical aspects such as mountains (affect wind and precipitation patterns), and sunlight exposure which impact the quantity of vegetation and how the climate exists.

• Proximity to water

Proximity to water influences local climate by moderating temperature. Because land heats up/cools down five times faster than water, the water is there to help regulate its temperature and prevent it from overheating/being too cold. 

• Altitude

The higher the altitude, the cooler the climate (containing less heat energy). This is because higher altitudes contain less air density. Less air density is the result of fewer heat-generating particle collisions in the atmosphere.

• Coriolis Effect/Jet Streams

The combination of the Coriolis Effect and convection allows for stable wind patterns, locally. Jet stream influences local climate by existing as the effect of extreme temperature differences and the Coriolis Effect. They exist as rapid, narrow, East flowing winds.

3. In your own words, explain how greenhouse gases cause the temperature of the atmosphere to increase

Greenhouse gases cause the temperature of the atmosphere to increase because they trap heat in the atmosphere, which heats up the earth. The more concentrated the gases are as they exist in the atmosphere, the warmer the planet will get.

4. Give 3 examples of natural processes that cause an increase in greenhouse gases.

1. Volcanic eruptions: volcanoes release carbon dioxide (CO2), as well as other gases, into the atmosphere. 

2. Decomposition of organic matter: natural decomposition processes, particularly in wetlands and other environments where organic matter breaks down without sufficient oxygen, releases methane. 

3. Release of methane from wetlands: wetlands are a significant natural source of methane. Microorganisms in these environments break down organic matter in anaerobic conditions, producing methane as a byproduct.

5. Give 3 examples of natural processes that remove greenhouse gases from the atmosphere.

1. Photosynthesis: plants, algae, and some bacteria use photosynthesis to convert carbon dioxide and water into sugars for energy. In this process, they absorb CO2 from the atmosphere and release oxygen. 

2. Absorption by the oceans: the oceans act as a massive carbon sink, absorbing a substantial portion of atmospheric CO2. CO2 dissolves in seawater, and through various chemical reactions, it is stored in the ocean. 

3. Weathering of rocks: chemical weathering of rocks, particularly silicate rocks, removed CO2 from the atmosphere over long timescales. When rainwater, which naturally contains dissolved CO2, reacts with these rocks, it forms carbonates, which can be carried to the ocean and eventually stored in sediments. 

6. Rank the following time periods (period, era, epoch, eon) from shortest to longest and then explain why 2 different epochs might last for different periods of time.

Shortest:

Epoch

Period

Era

Eon

Longest

Epochs, like all divisions of the geological time scale, are defined by significant geological or paleontological events. These events can vary greatly in duration and impact. 

7. If all of Earth’s history was represented by a clock, at what “time” would the dinosaurs have first appeared?  What time would they have gone extinct?

To preface, Dinosaurs first appeared in the Triassic Period, which began roughly 230 million years ago. When Earth's 4.5 billion years are compressed into a 12-hour clock, we’re essentially scaling down an immense amount of time. Based on this scale, the first dinosaurs appearance would appear very late in the day. 

So, dinosaurs would have arrived at roughly 11:20 to 11:30 pm. 

8. Describe each of the following in your own words and then explain how they can be used to determine the relative date of a sample.

• The Principle of Superposition

The principle of superposition states that in an undisturbed sequence of sedimentary rock layers, the youngest rocks will be at the top and the oldest rocks will be at the bottom. 

• Original Horizontality

The principle of original horizontality states that sedimentary rock layers are deposited as horizontal or nearly horizontal layers.

**If a rock layer is titled, it has been disturbed over time.

• Cross-cutting Relationships (Intrusions)

Cross cutting states that the intruding layer must be younger than the layers that it went through. 

**Sometimes, sedimentary rocks have igneous (volcanic) rock layers that cut across the layers. These igneous rocks are called intrusion.

• Unconformities

**Sedimentary rock is like a book to the past. However, sometimes there are layers missing, or the layering pattern has changed. These are typically a result of erosion.

Such breaks in the rock record are called unconformities.

• Fossil Correlation (Index Fossils)

Fossils that were widespread, but lived for a short period are called index fossils. 

**Since different species have existed at different times on Earth, when a rock layer in Section A has a known date..

That same date can be applied to similar fossils in other areas.

9. Explain the difference between Relative Dating and Absolute Dating.

Absolute dating is the process of assigning an exact numerical age to an organism, object, or event. Radioactive dating is an example of absolute dating, and can measure the age of objects from seconds to 10+ billion years. 

Relative dating is a method of determining the chronological order of events in geological history without necessarily determining their absolute age. Geologists use many rules to infer the relative age of rock layers. The list includes: the principle of superposition, original horizontality, cross-cutting relationships, unconformities, and fossil correlation. 

10. Explain why Carbon-14, which has a half-life of 5730 years, cannot be used to date fossils.  Make sure to give 2 reasons.

Carbon-14 dating is a powerful tool, but it has limitations that prevent it from being used to date most fossils. Here’s why: 

1. Short Half-Life:

Carbon-14 has a relatively short half- life of approximately 5,370 years. This means that after 5,370 years, half of the original carbon-14 in a sample will have decayed. After another 5,730 years, half of the remaining carbon-14 will have decayed. After about 50,000 to 60,000 years (roughly 10 half-lives), the amount of carbon-14 remaining in a sample becomes so small that it’s extremely difficult to measure accurately. Most fossils are significantly older than this limit, often millions of years old. Thus, there is not enough C14 left to measure. 

2. Organic Material Required:

Carbon-14 dating works by measuring the decay of carbon-14 in organic materials. This means that the sample being dated must have once been living. Fossilization often replaces the original organic material with minerals, effectively turning the organism into stone. So, the original carbon is gone, and replaced with other minerals. Therefore, there is no carbon 14 to measure. 

11. A particular radioisotope found in sandstone has a half life of 450,000 years.  If a sample of sandstone only has 12.5% (one eighth) of the expected amount of this isotope remaining, how old is it?

(Multiply the number of half lives by the half life duration: 3 half lives * 450,000 years/half-life= 1,350,000 years)

So, the sandstone sample is 1,350,000 years old.

12. Describe the Great Oxygenation Event and explain how it led to a mass extinction as well as the formation of some of the largest iron ore deposits in the world.

The earliest known catastrophe to species on Earth is called The Great Oxygenation Event. This occurred 2.4 billion years ago, when bacteria were starting to become more complex. 

Bacteria and Eukaryotes that could photosynthesize quickly took over as dominant organisms.

As oxygen was produced, carbon dioxide was removed from the atmosphere. 

The Oxygen produced quickly bonded to metals, most specifically LG iron. This is something referred to as the “mass rusting” event, and formed the major iron (III) oxide formations all over the world. Some of the most notable formations are in Minnesota, Michigan, Southern Ontario, and in Western Australia’s Pilbara region. 

The removal of too much CO2 cooled the Earth so much that the Earth nearly froze over. This killed a majority of the organisms on Earth at the time, except those at the equator. Those organisms are confined to produce iron (III) oxide bands, eventually producing the largest iron formations on Earth.

13. Describe how each of the following can impact Earth’s climate.

• Changes in Frequency of Volcanic Activity

Volcanic activity can have significant, though complex, impacts on Earth’s climate. Volcanic activity influences climate through cooling and warming effects. 

For the cooling effects: large volcanic eruptions release substantial amounts of sulfur dioxide into the stratosphere. In the stratosphere, SO2 converts to sulfuric acid aerosols, which reflect sunlight back into space. This results in a temporary cooling effect on Earth’s surface. 

For warming effects, volcanoes also release CO2 into the atmosphere, which warms the earth. Volcanic eruptions also release water vapor, which is a greenhouse gas. 

• Changes in Earth’s Axis

The impacts on climate are ice ages, seasonal variations, and long-term climate trends. 

Ice ages: Milankovitch cycles are believed to be a primary driver of ice ages. The combined effects of these cycles can alter the distribution of sunlight, leading to periods of cooler summers at high latitudes, which can allow ice sheets to grow. 

Seasonal variations: changes in axial tilt directly influence the intensity of timing of seasons. These variations can affect regional climates, influencing temperature patterns, precipitation, and vegetation. 

• Changes in the Shape of Earth’s Orbit

Changes in the shape of the orbit affects the amount of solar radiation Earth receives, contributing to long-term climate variations. It impacts solar radiation (the amount of sunlight more intense or less) received on Earth. 

• Timing of the Seasons with Respect to Earth’s Distance from the Sun.

The impacts on the climate are the hemispheric differences, long-term climate variability, and influence on regional climates. 

Hemispheric differences: influences the differences in seasonal extremes. 

Long-term climate variability: they affect the distribution of solar radiation across Earth’s surface, which influences temperature patterns and ice sheet growth. 

In essence, the timing of the seasons relative to Earth’s distance from the Sun modifies the intensity of seasonal solar radiation, leading to changes in the strength of seasonal contracts. 

14. Explain how samples of the ancient atmosphere obtained from ice cores led to alarm regarding the current level of carbon dioxide in the atmosphere.

They may cause alarm because they show a lack of historical stability (levels fluctuating), unprecedented spike (a dramatic and unprecedented surge in CO2), human fingerprints (aligns with the Industrial Revolution and the increased burning of fossil fuels, indicating a clear human influence), and a climate change threat (shows that we are heading into severe and unpredictable consequences). 

15. Describe how each of the following methods can be used to study the climate of the past.

• Tree Rings

This is a short term process. 

Samples are taken from old living trees and preserved dead trees. Most trees grow faster in warm weather and slower in cold weather. 

• Ancient Pollen

This is a medium term process. 

Pollen blown from plants is trapped in mud. More pollen from warm-weather plants means warmer climates, more from cold-weather plants mean colder climates. 

Law of superposition applies!

• Ice Core Data

This is a long term process. 

Basically, ice cores have layers like tree rings. Atmospheric gases get trapped in bubbles in these ice cores. CO2 amounts can be measured directly from ice cores. Ratios of different oxygen isotopes helps determine temperature.