Introduction to Marine Science - Chapter 4 hw

Before the 1980s, the K-T mass extinction was a mystery. Scientists wondered if it was due to disease or climate change or even volcanic activity. Another hypothesis was that Earth experienced an impact of a giant extraterrestrial meteor. Researchers wanted to test these different hypothesis by gathering evidence. Luis and Walter Alvarez and their team scientists set out to measure the amount of cosmic dust in the K-T boundary.

- Scientist discovered a meteorite impact crater that was at least 10 KM in diameter, which would be large enough to explain a global cloud of debris large enough to cause a mass extinction - scientist sampled boundary sediments that contain high concentrations of the element iridium (Ir), which is rare in earth rocks but abundant and meteorites - Scientists sampled boundary sediments that contained shocked quartz grains, which would indicate that an event with enough force to fracture and partially melt pieces of quartz had occurred

Luis and Walter Alvarez found that the KT boundary sediments in Italy contain high amounts of the element iridium. This element is very uncommon and terrestrial rocks but highly concentrated in meteorites, suggesting that an impact from a large 10 KM diameter meteorite had occurred at that time. Their results shocked the geological community. On the basis of this finding, they hypothesized that the mass extinction at the KT boundary what is caused by the shut down of photosynthesis by a global cloud of impact debris. Final confirmation of the impact came in the early 1990s with the discovery that the 200 KM diameter Chicxulub Crater in the Yucatán Peninsula of Mexico is likely the site of this catastrophic event

- The meteorite impact ejected dust and debris into the atmosphere, which probably caused the earths surface to cool - The meteorite impact ejected dust and debris into the atmosphere which probably blocked the sun and limited photosynthesis. - Geologists collected many sediment cores from the sea floor that showed how earth has experienced many such extraterrestrial impacts over geologic time. - acid rains and global fires probably added to the environmental disaster thereby causing extinction of the dinosaurs and many other species.

SmartFigure: Characteristics of water above and below the calcite compensation depth (CCD) The tests from which of the following organisms will dissolve below the CCD?

- coccolithophores - foraminifera

SmartFigure: Characteristics of water above and below the calcite compensation depth (CCD) What conditions exist below the CCD?

- cold temperature - high acidity - high carbon dioxide concentration

What sediment type(s) is/are included in the pink category labeled "Other" on the map?

-cosmogenous sediments -hydrogenous sediments

What mechanism(s) is/are responsible for transporting clay to deep ocean basins?

-wind -slow-moving ocean currents

_______: in the decade that followed the Alvarez paper, hundreds of studies of K-T boundary deposits from cores of sea floor sediment around world documented the global fallout of impact debris. _______: collecting many samples from cores of sediment from the seafloor, which contained proportions of iridium and shocked quartz grains. ________: Luis and Walter Alvarez speculated that earth experienced an extra terrestrial impact of a giant meteor. ________: The boundary sediments contained huge amounts of iridium that could only be explained by the impact on earth of a 10 KM diameter meteorite. _________: Louis and Walter Alvarez determined that their hypothesis was correct, that the mass extinction at the KT boundary was caused by the shut down of photosynthesis by a global cloud of impact debris. _________: Luis and Walter Alvarez publication of their findings revolutionized geology.

1. Replication 2. Observation 3. Hypothesis 4. Results 5. Conclusion 6. Communication

SmartFigure: Characteristics of water above and below the calcite compensation depth (CCD) What is calcareous ooze composed of?

At least 30% the remains of calcareous organisms.

Animation: Calcareous Ooze and the Calcite Compensation Depth What would happen if the depth of the CCD were above the top of the mid-ocean ridge?

Calcareous ooze would not be found below the CCD.

Chemical reactions within seawater cause certain minerals to come out of solution, or precipitate, they change from the _____ state to the ______ state.

Dissolved; solid

SmartFigure: Characteristics of water above and below the calcite compensation depth (CCD) In which setting would calcareous ooze be most likely to form?

On the crest of a seamount under warm surface water

How does siliceous ooze accumulate on the seafloor if silica-based residues are dissolved slowly at all depths?

Silica tests accumulate faster than seawater can dissolve them.

SmartFigure: Characteristics of water above and below the calcite compensation depth (CCD) Where do calcareous oozes exist on the seafloor?

Underneath areas where calcareous organisms live, above the CCD.

Animation: Calcareous Ooze and the Calcite Compensation Depth What is calcareous ooze?

a fine-grained, deep ocean sediment containing the skeletal remains of calcite-secreting microbes

The most likely place to find abundant manganese nodules is on the:

abyssal plain far from a continent

What factor primarily determines the distribution of radiolarian ooze?

areas of upwelling

Sediments derived from the remains of the hard parts of once-living organisms are called __________ sediments.

biogenous

Which type of marine sediments include siliceous and calcareous oozes?

biogenous

Marine sediments that originate in the warm tropical surface ocean would create deposits in the deep sea composed primarily of _________.

calcium carbonate

Mobile Interactive Animation: Accumulation of Siliceous Ooze Two common types of chemical compounds found in biogenous sediments are _______ and ________.

calcium carbonate and silica

Phosphate-rich nodules form in:

intermediate to shallow depth water.

Abyssal clay contains ________.

iron

Volcanic ash is considered to be which type of marine sediment?

lithogenous

Sort the following statements into "Supported by data" or "Not supported by data."

Supported by data: - KT boundary sediments around the world also contain high amounts of iridium that could only be explained by the impact on earth of a 10 KM in diameter meteorite - The shut down of photosynthesis by the global cloud of impact debris caused the mass extinction documented at the KT boundary - marine deposits in northern Italy from the KT boundary contained and unusual clay layer with high proportions of iridium and shocked quartz grains which are only formed during an intense impact - Computer models indicated that a meteor impact would produce a global aerosol cloud for about 12 years and black out over 50% of the sunlight - the aerosols produced by the meteor impact drench the surface with the sulfuric acid rain Not supported by data: - Computer models predicted that smoke and dust from a meteor impact would warm the earth too much.

The sea floor provides the largest reservoir of usable energy in the ocean, and likely the world, in the form of ______________.

clathrates

SmartFigure: Distribution of Neritic and Pelagic Sediments Which sediment type dominates in the neritic environment?

coarse lithogenous sediment, such as sand and small rocks

Sediments with an extraterrestrial origin are called:

cosmogenous

Animation: Calcareous Ooze and the Calcite Compensation Depth What three steps are required for calcareous ooze to exist below the CCD?

deposition of calcite shells above the CCD, cover of these shells by a non-calcareous material, and movement of the sea floor over millions of years

Mobile Interactive Animation: Accumulation of Siliceous Ooze The two major types of microscopic, planktonic organisms that produce siliceous oozes are ______ and ______.

diatoms and radiolarians

Sediments that are poorly sorted were most likely deposited by:

glacier

Siliceous ooze is particularly abundant on the seafloor at __________ and at __________.

high latitudes; equatorial upwelling zones

Sediments produced because of chemical reactions in seawater are called:

hydrogenous

Animation: Calcareous Ooze and the Calcite Compensation Depth What is the calcite compensation depth, or CCD?

the ocean depth below which calcite is unstable and will dissolve quickly

What factor primarily controls the distribution of calcareous ooze?

water depth