1

1

4

2

2

1

2

3

4

2

2

1

1

3

3

1- By using index fossil.
2- Radioactive decay dating.
3- Correlation by matching sequences of rock layers.

The thick wavy line (in red) represents the unconformity or buried erosion surface, between two layers in column A.

We can note that the succession of the rock layers in column A and B are same, except for a missing rock layer in column A. In column B, we can see that there is a layer (4th layer from the bottom) that is not present in column A. This indicates that after the deposition of the third layer in column A, there was a period of erosion, and there was no deposition, which represents the unconformity.

The limestone layers protrude farther. there is less evidence of erosion to the limestone layers.

542 million years

Paleozoic Era and Carboniferous period.

1-Photosynthetic life forms.
2-Plants.
3-Bacteria.

Can cause isolation of land ares resulting in independent evolution. can cause an increase of marine environments compared to land environments.

During the Silurian this area was hot and dry and there was much evaporation of an ocean or sea forming salt and gypsum. today the conditions are warm and humid

1- A dust could caused by the impact cooled earth resulting in an ice age.
2- Fires from the impact burned much of earth’s surface.
3- Acid precipitation killed most of the vegetation.

Earth was likely melted at this time and gravity caused the more dense part, such as iron to move toward the core of earth.

The age of our solar system and earth (4.6 billion years) is younger than the most distant galaxies (12 billion years).

Sedimentary rock or any clastic or bioclastic sedimentary rock

Paleozoic Era.

1- siltstone. (the oldest)
2- limestone.
3- granite intrusion.
4- shale.
5- vascular basalt.
6- sandstone. (the youngest)

Permian.

Marble.

Between the shale and limestone or/and the granite intrusion.

Only on earth are surface temperatures, for most of the planet. neither too hot nor too cold for life as we know it. Also, earth temperatures and pressures allow for liquid water to exist, conditions that don’t exist on the other planets . free oxygen in a high density exists only on earth and much earth life requires this oxygen.

If magma intrudes a sandstone and the magma is near the solidification temperature, ans then a piece of sandstone falls into the magma, it will become an inclusion and not be melted.

New radon is constantly being produced by the radioactive decay of uranium which has an extremely long half-life.

Radon gets concentrated in basements is likely due to the high density of radon compared to normal air and thus the radon sinks into the basements or just doesn’t rise out of the basements naturally.

Radon would not be suitable for use in normal radioactive dating because of its very short (four days) half-life, there would be too little left after a few years to be able to measure an event accurately. if you were trying to measure events of only hours to weeks old, them radon may be useful.

A home owner in the reading prong could make sure that the parts of the home below ground level are sealed tightly and made impermeable to radon. A home owner could also use a forced-air moving system to constantly remove air, including radon, from the home.

3

2

2

Triassic period.

they have only been found in a narrow geographic range.

Use the law of superposition to compare the age with the age of other nearby fossils and/or rock layers, radioactive age dating (not C-14)

The cross sections below show widely separated outcrops at locations W, X, Y, and Z. The rock layers have not been overturned or deformed. Fossils are shown in some of the rock layers.

We can apply the principle of superposition which states that in an undeformed sequence of sedimentary rocks, each layer of rock is older than the one above it and younger than the one below it.

To determine the relative geologic age of the four fossils, we will correlate the rock layers between these outcrops. We will match the same sedimentary rock types, and the fossil types. The igneous intrusion layers can be used as reference.

From the correlation, we can see that the oldest fossil is the trilobite fossil in the shale rock layer. The second oldest fossil is the crinoid fossil found in the sandstone layer. The third oldest fossil is the ammonite fossil in the shale layer. Lastly, the youngest fossil is the brachiopod fossil in the sandstone layer.

The features include:
– Submergence.
– Uplift.
– Weathering.
– Erosion.
– Deposition.
– Burial.

Formed by on of these features:
– Unconformity.
– Time gap in the rock record.
– Buried erosional surface.

– By heat and pressure.
– Recrystallizing of preexisting rock.
– Metamorphism.

– Cooksonia.
– Hexameroceras.

The encircled letter is letter I, which is the oldest rock unit shown in the cross section.

Layer H is on top of layer I. The Law of Superposition supports that rock layer I is older than rock layer H. This law states that in a sequence of sedimentary rock layers, the layer at the bottom of a sequence is the oldest, and the layer at the top is the youngest. However, only rock layer H is a sedimentary rock, and rock layer I is an igneous rock.

To support our answer, rock layer I and rock layer H have an unconformity represented by the wavy line. Unconformities are break in the stratigraphic record wherein there is a surface of erosion or non-deposition. In this case, since the rock units are tilted, this is called angular unconformity. We can see the angular relationship of layers I and H that were originally deposited horizontally.

But since rock layer I is an igneous rock, these are not formed through deposition. To further support our answer, the specific unconformity in rock layer I is called non-conformity. This occur where igneous rocks or metamorphic rocks are overlain by sedimentary rocks formed at the Earth’s surface. This only occur when all the rocks overlying the metamorphic or intrusive igneous rocks have been removed by erosion.

After the non-conformity in rock layer I, rock layer H was deposited. Therefore, rock layer I is older than rock layer H.

I

On the cross section below, the area with X symbols indicates the location where marble was formed.

The high temperature and pressure by the intrusive body F results in the contact metamorphism between the rock layers it reaches. This melts the pre-existing rocks and minerals crystallize as the melt cools. The minerals grow larger and fuse together forming metamorphic rocks.

Marble is a metamorphic rock formed from pre-existing limestone rock that is exposed to extreme temperatures and pressures. The limestone layer in the cross section is represented by brick pattern symbol. Therefore, the area where marble was formed is in the region of contact metamorphism between the intrusive body F and the limestone layer.

The cross-section below shows a portion of Earth’s crust.

One piece of evidence shown in the cross section that suggests rock unit D is younger than rock unit F is that, rock unit F did not cut across rock unit D. This is supported by the Principle of Cross-cutting Relations which states that younger features such as faults, dikes, etc. cut across older features.

Another evidence is that we can see from the cross section that rock unit F was eroded when rock unit D was formed, as represented by a buried erosional surface. Since rock unit rock unit D is on top of rock unit F, we can prove that rock unit D is younger than rock unit F, according to the Principle of Superposition.

Rock unit F did not cut across rock unit D.

The cross-section below shows a portion of Earth’s crust.

Rock unit H is not one continuous layer because it was cut and displaced by movement along a fault, probably when an earthquake or a tectonic event occurred.

Rock unit H is not one continuous layer because it was cut and displaced by a fault.