Question

ordering geologic events based on rock layers

number the events (1-4) based on the order that they happened, with 1 being the first thing that happened and 4 being the last.

☐ magma cut into the red-brown rocks and solidified to form glasslike rocks.

☐ red-brown rocks with sand-sized rock grains were deposited horizontally.

☐ rocks composed of gray clay flakes with crystals of minerals were deposited horizontally.

☐ rocks made of shell and skeletons of marine organisms were deposited horizontally.

image of outcrop labeled outcrop

Explanation:

To solve the problem of ordering geologic events based on rock layers, we use the principle of superposition (older layers are at the bottom, younger at the top) and cross - cutting relationships (a feature that cuts through rocks is younger than the rocks it cuts).

Step 1: Identify the oldest depositional event

Depositional events happen in a bottom - to - top order (older at the bottom). The rocks made of shell and skeletons of marine organisms are at the bottom (from the outcrop image's bottom layer). So this event (Rocks made of shell and skeletons of marine organisms were deposited horizontally) is the first to occur. Let's assign it a number of 1.

Step 2: Next depositional event

The next layer up is the red - brown rocks with sand - sized rock grains. Since it is deposited on top of the marine organism - based rocks, it is younger than the marine organism - based rocks but older than the layers above it. So the event (Red - brown rocks with sand - sized rock grains were deposited horizontally) is the second event. We assign it a number of 2.

Step 3: Next depositional event

The layer above the red - brown rocks is the rocks composed of gray clay flakes with crystals of minerals. It is deposited on top of the red - brown rocks, so it is younger than the red - brown rocks. The event (Rocks composed of gray clay flakes with crystals of minerals were deposited horizontally) is the third event. We assign it a number of 3.

Step 4: Cross - cutting event

The magma that cut into the red - brown rocks (and solidified to form glasslike rocks) cuts through the red - brown rocks. By the cross - cutting relationship principle, this event is younger than the red - brown rocks (and thus younger than the previous depositional events). So the event (Magma cut into the red - brown rocks and solidified to form glasslike rocks) is the last event. We assign it a number of 4.

So the order of the events from 1 (first) to 4 (last) is:

1. Rocks made of shell and skeletons of marine organisms were deposited horizontally.
2. Red - brown rocks with sand - sized rock grains were deposited horizontally.
3. Rocks composed of gray clay flakes with crystals of minerals were deposited horizontally.
4. Magma cut into the red - brown rocks and solidified to form glasslike rocks.

If we represent the events with their respective numbers in the dropdowns (from top to bottom of the event list in the problem):

• For "Magma cut into the red - brown rocks and solidified to form glasslike rocks": 4
• For "Red - brown rocks with sand - sized rock grains were deposited horizontally": 2
• For "Rocks composed of gray clay flakes with crystals of minerals were deposited horizontally": 3
• For "Rocks made of shell and skeletons of marine organisms were deposited horizontally": 1

Answer:

To solve the problem of ordering geologic events based on rock layers, we use the principle of superposition (older layers are at the bottom, younger at the top) and cross - cutting relationships (a feature that cuts through rocks is younger than the rocks it cuts).

Step 1: Identify the oldest depositional event

Depositional events happen in a bottom - to - top order (older at the bottom). The rocks made of shell and skeletons of marine organisms are at the bottom (from the outcrop image's bottom layer). So this event (Rocks made of shell and skeletons of marine organisms were deposited horizontally) is the first to occur. Let's assign it a number of 1.

Step 2: Next depositional event

The next layer up is the red - brown rocks with sand - sized rock grains. Since it is deposited on top of the marine organism - based rocks, it is younger than the marine organism - based rocks but older than the layers above it. So the event (Red - brown rocks with sand - sized rock grains were deposited horizontally) is the second event. We assign it a number of 2.

Step 3: Next depositional event

The layer above the red - brown rocks is the rocks composed of gray clay flakes with crystals of minerals. It is deposited on top of the red - brown rocks, so it is younger than the red - brown rocks. The event (Rocks composed of gray clay flakes with crystals of minerals were deposited horizontally) is the third event. We assign it a number of 3.

Step 4: Cross - cutting event

The magma that cut into the red - brown rocks (and solidified to form glasslike rocks) cuts through the red - brown rocks. By the cross - cutting relationship principle, this event is younger than the red - brown rocks (and thus younger than the previous depositional events). So the event (Magma cut into the red - brown rocks and solidified to form glasslike rocks) is the last event. We assign it a number of 4.

So the order of the events from 1 (first) to 4 (last) is:

1. Rocks made of shell and skeletons of marine organisms were deposited horizontally.
2. Red - brown rocks with sand - sized rock grains were deposited horizontally.
3. Rocks composed of gray clay flakes with crystals of minerals were deposited horizontally.
4. Magma cut into the red - brown rocks and solidified to form glasslike rocks.

If we represent the events with their respective numbers in the dropdowns (from top to bottom of the event list in the problem):

• For "Magma cut into the red - brown rocks and solidified to form glasslike rocks": 4
• For "Red - brown rocks with sand - sized rock grains were deposited horizontally": 2
• For "Rocks composed of gray clay flakes with crystals of minerals were deposited horizontally": 3
• For "Rocks made of shell and skeletons of marine organisms were deposited horizontally": 1