Why in News?
A groundbreaking study by German researchers has revealed that precious metals like gold, platinum, and ruthenium are leaking from Earth’s core to the surface through volcanic activity. This challenges the long-standing belief that the core is geochemically sealed off from the mantle and crust. The findings come from isotope analysis of volcanic rocks from Hawaii, showing evidence of core-mantle material exchange, particularly via mantle plumes.
Core-Mantle Interaction: Key Findings
| Aspect | Details |
|---|---|
| Study Focus | Volcanic rocks from Hawaii formed by mantle plumes rising from the core-mantle boundary |
| Isotopic Evidence | Presence of ruthenium-100 (^100Ru), mainly found in Earth’s core |
| Main Conclusion | Confirms material from the core reaches the surface, implying stronger connectivity between core and mantle |
Precious Metals in the Core
| Metal | Presence & Significance |
|---|---|
| Gold | Over 99.999% believed to be trapped in the Earth’s core |
| Ruthenium | Core-specific isotope (Ru-100) found in surface rocks—key evidence of upward movement |
| Platinum, Iridium | Also siderophile elements concentrated in the core, previously considered inaccessible |
Earth’s Mantle: Key Features
| Feature | Details |
|---|---|
| Volume & Depth | Covers 83% of Earth’s volume, from Moho (7–35 km) to 2,900 km depth |
| Composition | Silicate-rich rocks: olivine, garnet, pyroxene; elements: O (45%), Si (21%), Mg (23%) |
| Density | 2.9–3.3 g/cm³ (upper mantle); 3.3–5.7 g/cm³ (lower mantle) |
| Temperature | Ranges from ~200°C (near crust) to ~4,000°C (core boundary) |
| Convection | Heat-driven circulation enables plate tectonics |
| Seismicity | Earthquakes occur within the mantle, especially in subduction zones (up to 670 km depth) |
Earth’s Core: Structural Insights
| Layer | Details |
|---|---|
| Outer Core | 2,900–5,150 km deep; liquid iron-nickel; temperature: 4,000–6,000°C; drives magnetic field |
| Inner Core | 5,150–6,371 km deep; solid iron-nickel; extremely dense; rotates slightly faster than Earth’s crust |
| Conductivity | High thermal and electrical conductivity; contributes to magnetic field and internal heat transfer |
| Boundary | Inner core separated from outer core by Lehmann Discontinuity |
Asthenosphere: Upper Mantle Engine
| Aspect | Details |
|---|---|
| Depth | 80–200 km, beneath lithosphere |
| Properties | Ductile, weak, highly viscous; denser than crust |
| Role | Allows tectonic plate motion; source of magma for volcanic eruptions |
In a Nutshell
Memory Code: “CAMP GOLD”
| Mnemonic Element | What it Stands For |
|---|---|
| C – Core leaks | Core not sealed: material exchange with mantle confirmed |
| A – Asthenosphere | Ductile mantle layer helps in tectonics and magma movement |
| M – Mantle plume | Hawaii rocks show plume transport from core-mantle boundary |
| P – Precious | Gold, Ruthenium, Platinum in the core surface via plumes |
| GOLD | Gold in Core > 99.999%; study reveals leakage to crust |
Prelims MCQs
Q1. Consider the following statements about Earth’s Mantle:
- It is primarily composed of silicate rocks rich in magnesium and iron.
- Mantle convection is driven by temperature differences between crust and core.
- The mantle constitutes less than half of Earth’s total mass.
Which of the above statements is/are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3
Q2. With reference to Earth’s Core, consider the following statements:
- The inner core is liquid while the outer core is solid.
- The Earth’s magnetic field is mainly generated by the movement of molten iron in the outer core.
- The core is geochemically isolated with no interaction with the mantle.
Which of the statements given above is/are correct?
A. 1 only
B. 2 only
C. 2 and 3 only
D. 1 and 2 only
Q3. Consider the following statements:
- Ruthenium-100 is primarily a crustal isotope, found mostly in surface rocks.
- The asthenosphere is mechanically weak and helps tectonic plates move.
- The presence of siderophile elements in surface volcanic rocks indicates material leakage from Earth’s core.
Which of the statements are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1 and 2 only
D. All of the above
Mains Questions
- Recent geological findings suggest material exchange between Earth’s core and surface. Discuss the implications of such a discovery on our understanding of Earth’s geochemical evolution. (GS1 – Geography)
- Explain the role of asthenosphere in plate tectonics and how its physical properties make it a key player in Earth’s internal dynamics. (GS1 – Geography)
Prelims MCQ Answers & Explanations
| Q No. | Correct Answer | Explanation |
|---|---|---|
| Q1 | A. 1 and 2 only | Statement 1 is true (silicate + Mg/Fe). Statement 2 is true (core-crust temp difference drives convection). Statement 3 is false (mantle = 67% mass). |
| Q2 | B. 2 only | Statement 1 is false (inner core is solid, outer is liquid). Statement 2 is true (outer core drives magnetic field). Statement 3 is false (core leaks). |
| Q3 | A. 2 and 3 only | Statement 1 is false (Ru-100 is a core isotope). Statement 2 is true (asthenosphere is weak & ductile). Statement 3 is true (Ru-100 found in surface). |
