ENV 100 - Modules 4-6

Resurfacing the planet, unprecedented changes, providing for our future.

Resurfacing

Processes that act on Earth’s surface to facilitate the creation, erosion, transportation, and deposition of sediment.

What kinds of processes can be included in resurfacing?

Physical, chemical, biological.

A-axis

The long side of a grain of sediment.

B-axis

The intermediate side of a grain of sediment.

C-axis

The short side of a grain of sediment.

Which axis is used to classify the size of a particle?

The B-axis.

What processes form sedimentary rocks? 

Weathering

Erosion

Transortation

Deposition

Lithification

What kind of sedimentary rocks are formed by rounded gravels/pebbles?

Conglomerate. 

What kind of sedimentary rocks are formed by angular gravels/pebbles?

Breccia.

What kind of sedimentary rock is formed from sand?

Sandstone.

What are the three types of sandstone? 

Fine, medium, coarse. 

What kind of sedimentary rocks are formed from silt?

Siltstone.

What kinds of sedimentary rock are formed from silt and clay?

Mudstone and shale.

The higher the energy of an environment, the ____ the clasts in the sedimentary rock will be. 

larger

The lower the energy of an environment, the ____ the clasts in the sedimentary rock will be.

smaller

Why do higher energy environments have larger clasts?

They are able to transport the larger clasts.

Clast

A fragment of rock.

What (non-sedimentary) processes are involved in resurfacing? 

Volcanism, mass movement, glaciation, asteroid impacts. 

When did the Chicxulub asteroid impact Earth?

66 MYA.

What was the diameter of the Chicxulub asteroid?

17km.

What was the diameter of the crater from the Chicxulub asteroid impact?

100km.

How much sulphur was released into the atmosphere by the Chicxulub asteroid impact?

325 billion tonnes.

What angle did the Chicxulub asteroid impact at? 

60 degrees. 

What evidence is there for the Chicxulub asteroid impact?

Gravity anomalies, tektites, wildfires, tsunami and sedimentary evidence.

Gravity anomalies

Places on Earth where gravity is different from that of a smooth, featureless Earth.

Where were tektites found? 

In the gills of fossilised fish. 

Tektites

Small pieces of glass formed from melting of rock during a meteorite impact.

What is the wildfire evidence from the Chicxulub asteroid impact?

Charcoal left behind in the peak ring of the crater.

What evidence is there of a tsunami caused by the Chicxulub asteroid impact? 

Unusual sedimentary structures and grains, out-of-place fossils. 

What would the tsunami following the Chicxulub impact have been like?

An oscillating tsunami that lasted a long time.

What sedimentary tsunami evidence of the Chicxulub impact was found at Brazos River, Texas?

A sandstone layer inside mudstone, paleontological indicators, iridium anomalies.

Why was finding sandstone inside of mudstone unusual? 

Sandstone is indicative of a higher-energy system, such as that created by a tsunami. 

Why was the finding of iridium important?

Iridium is rare on Earth but common in meteorites.

What was the sandstone at Brazos River like?

Coarse-grained with large clasts and networked carbonate nodules.

What sedimentary tsunami evidence of the Chicxulub asteroid impact was found at Arroyo el Mimbral, Mexico? 

Evidence of oscillating tsunami, thick boundary sediments, impact melt spherules, layer containing plant debris. 

Why was the layer containing plant debris unusual?

This area was around 500m underwater at the time, so this indicates backwash from the tsunami.

How much material entered the Chicxulub crater in the day after impact?

130m.

Graded bed

A sedimentary system that is sorted by size.

The sorted sediment in the peak ring of the Chicxulub crater is evidence of ____. 

flooding

What was found in the boundary clays of the Chicxulub crater?

Iridium, impact-shocked minerals, abrupt change in fossils.

What geological boundary did the Chicxulub asteroid impact occur at?

The Cretaceous-Paleogene (K-Pg) boundary.

What period ended with the Chicxulub impact? 

The Mesozoic period. 

What are some examples of species that went extinct following the Chicxulub asteroid impact?

Ammonites, dinosaurs excluding beaked birds.

Why did beaked birds survive the mass extinction?

They were able to better adapt to the abrupt change in food source.