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Zorluk: OrtaComparing and Contrasting Models

### Models of the Hawaiian-Emperor Seamount Chain Formation

The Hawaiian-Emperor seamount chain is a long line of volcanoes and seamounts stretching approximately 6,000 km6,000\text{ km} across the Pacific Ocean. The ages of these volcanoes increase progressively from 0 million years0\text{ million years} (active volcanoes in the southeast) to over 80 million years80\text{ million years} (eroded seamounts in the northwest). Scientists propose two models to explain the formation of this volcanic chain.

#### Model 1
A stationary mantle plume—a localized upwelling of exceptionally hot rock—originates deep within Earth's mantle near the core-mantle boundary. As the Pacific Plate moves slowly northwestward over this fixed hotspot, magma penetrates the lithosphere, forming a series of volcanoes. The older volcanoes are carried away from the hotspot, becoming inactive and eroded over time, while new volcanoes form directly above the plume. The volcanic activity is driven solely by deep-seated thermal anomalies that are independent of plate boundaries or local tectonic stresses.

#### Model 2
The volcanic chain is caused by propagating fractures in the Pacific Plate itself, created by changes in plate motion and regional tectonic stresses. The Pacific Plate experiences tensional stress that causes the lithosphere to crack. As these cracks propagate southeastward over time, they depressurize the shallow mantle directly underneath, causing localized melting (decompression melting). Magma rises through the newly formed fractures to build volcanoes. The age progression is a result of the gradual propagation of the fractures, and no deep-seated, stationary mantle hotspot is involved.

According to the descriptions of the two models, Model 1 and Model 2 disagree on which of the following points?

  1. A
    Whether the Pacific Plate has experienced motion over time.
  2. Whether the volcanic activity is driven by a deep-seated thermal anomaly or shallow tectonic stress.Cevap
  3. C
    Whether the volcanic chain exhibits a progressive age gradient.
  4. D
    Whether the rising magma eventually reaches Earth's surface to form volcanoes.

Cevap

The correct answer states that the models disagree on whether the volcanic activity is driven by a deep-seated thermal anomaly or shallow tectonic stress.
The correct answer is correct because Model 1 describes a deep-seated thermal anomaly (mantle plume) near the core-mantle boundary as the driver, while Model 2 describes shallow tectonic stress causing fractures and decompression melting.

Adım Adım Çözüm

1
Analyze Model 1's mechanism for generating volcanic activity.
Model 1 asserts that volcanic activity is driven by a stationary mantle plume originating deep in the mantle (near the core-mantle boundary), representing a thermal anomaly independent of plate stresses.
To understand the proposed cause of volcanism in the first model.
2
Analyze Model 2's mechanism for generating volcanic activity.
Model 2 asserts that volcanism is caused by propagating fractures due to tectonic stresses and changes in plate motion, causing decompression melting in the shallow mantle.
To understand the proposed cause of volcanism in the second model.
3
Compare the two mechanisms to identify the main point of disagreement.
The models differ fundamentally on whether the driving force is a deep thermal anomaly (Model 1) or shallow plate fracture and stress (Model 2).
To find the correct option representing the disagreement between the two models.

Anahtar Kavram

Comparing and contrasting competing scientific models by identifying key differences in their underlying mechanisms and causal factors.
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Comparing and Contrasting Models

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