Geothermal heat flux (GHF) beneath the West Antarctic Ice Sheet (WAIS) is a subject of deb… — ACT

Geothermal heat flux (GHF) beneath the West Antarctic Ice Sheet (WAIS) is a subject of debate among geophysicists. Two researchers propose different explanations for the source and distribution of this geothermal heat.

Researcher 1
Geothermal heat flow is primarily driven by active crustal rifting and mantle magma migration in the West Antarctic Rift System (WARS). GHF is highly localized, exceeding $150\text{ mW/m}^2$ directly above active mantle plumes and fault lines, but dropping below $50\text{ mW/m}^2$ at distances greater than $10\text{ km}$ from these faults. The thickness, age, and mineral composition of the overlying granitic basement rock have no effect on GHF.

Researcher 2
Geothermal heat flow is driven by the decay of radiogenic isotopes ( $^{238}\text{U}$ , $^{232}\text{Th}$ , and $^{40}\text{K}$ ) within the continental crust. The granitic basement rock beneath the WAIS is thick and highly enriched in these isotopes. Thus, GHF is widely distributed and relatively uniform across the entire region, ranging from $70\text{ to }95\text{ mW/m}^2$ . Proximity to active rift faults or tectonic boundaries does not affect GHF.

A study measured the GHF at five borehole locations at varying distances from a major active fault line in the WARS. The granitic basement rock at all five locations has identical thickness and age. The results are shown in the table below:

Location	Distance from fault ( $\text{km}$ )	GHF ( $\text{mW/m}^2$ )
1	2	160
2	8	110
3	15	45
4	30	42
5	50	40

Based on the information provided, the measured GHF at these locations supports the viewpoint of which researcher, if either?

Researcher 1 only, because the GHF exceeded $150\text{ mW/m}^2$ near the fault and dropped below $50\text{ mW/m}^2$ at distances greater than $10\text{ km}$ .Cevap
B
Researcher 2 only, because the GHF was measured in regions with identical basement rock thickness and age.
C
Both Researcher 1 and Researcher 2, because the GHF values represent a uniform baseline that increases near fault lines due to magma migration.
D
Neither Researcher 1 nor Researcher 2, because the GHF values at all five locations remained between $70\text{ and }95\text{ mW/m}^2$ .

Cevap

Researcher 1 only, because the GHF exceeded

150\text{ mW/m}^2

near the fault and dropped below

50\text{ mW/m}^2

at distances greater than

10\text{ km}

The correct option is Researcher 1 only. The data shows that the GHF varies dramatically with distance from the fault line: it is extremely high (

160\text{ mW/m}^2

) within

2\text{ km}

of the fault, and it falls below

50\text{ mW/m}^2

at distances of

15\text{ km}

or more. This matches Researcher 1's predictions of localized heat flow concentrated near faults (

>150\text{ mW/m}^2

) and low heat flow (

<50\text{ mW/m}^2

) beyond

10\text{ km}

. It contradicts Researcher 2's prediction that GHF would be uniform and stay between

70\text{ and }95\text{ mW/m}^2

Adım Adım Çözüm

Analyze the predictions made by Researcher 1 and Researcher 2 regarding GHF distribution and magnitude.

Researcher 1 predicts high GHF (

>150\text{ mW/m}^2

) close to faults and low GHF (

<50\text{ mW/m}^2

) beyond

10\text{ km}

. Researcher 2 predicts a uniform GHF (

70\text{ to }95\text{ mW/m}^2

) unaffected by faults.

Establishing clear criteria for each viewpoint allows direct comparison with the empirical data.

Compare the measured GHF values at different distances from the fault in the table against the predictions.

Near the fault (

2\text{ km}

), GHF is

160\text{ mW/m}^2

(supports Researcher 1). Far from the fault (

>10\text{ km}

), GHF drops to

45\text{ mW/m}^2

42\text{ mW/m}^2

, and

40\text{ mW/m}^2

(supports Researcher 1). The GHF varies from

40\text{ to }160\text{ mW/m}^2

, which contradicts Researcher 2's prediction of a uniform range of

70\text{ to }95\text{ mW/m}^2

Testing the data points against each model's limits determines which model is supported or weakened.

Determine which researcher is supported and select the corresponding option.

Only Researcher 1's predictions are aligned with the borehole data.

This completes the evaluation of the viewpoints based on the new evidence.

Anahtar Kavram

Aligning experimental data with conflicting scientific hypotheses

Soru

Cevap

Adım Adım Çözüm

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