The Planet Earth

Analyzing solar system elemental abundances:

(A) - Hydrogen (~73% by mass, ~92% by number) and Helium (~25% by mass, ~8% by number) are by far the most abundant elements in the solar system. Together they comprise about 98% of all matter. This reflects the primordial composition from the Big Bang and stellar nucleosynthesis.

(B) - There is a general exponential decrease in elemental abundance with increasing atomic number from H (Z=1) through the first 50 elements. This trend reflects:

• The decreasing efficiency of stellar nucleosynthesis for heavier elements
• The exponentially greater energy required to fuse heavier nuclei
• While there are local variations (peaks and valleys), the overall trend from Z=1 to Z=50 is strongly decreasing

(C) - This is false. Elements heavier than iron (Z=26) and certainly those above Z=50 are significantly less abundant than lighter elements. Heavy elements (>50) are produced through slow and rapid neutron capture processes (s-process and r-process) which are much rarer than the fusion processes creating lighter elements. The abundances continue to decrease for heavier elements.

(D) - This is the opposite of reality. The Oddo-Harkins rule states that elements with even atomic numbers are generally more abundant than their odd-numbered neighbors. This occurs because:

• Even-Z nuclei have paired protons, making them more stable
• Stellar nucleosynthesis favors production of even-Z elements through alpha-particle capture
• Odd-Z elements show lower abundances due to lower nuclear stability

Answer: (A) and (B) are correct

To solve this problem, we must match the countries in Group I with the plate tectonic features in Group II that cause seismic activity.

1. Iceland, known for its volcanic activity, is located on the Mid-Atlantic Ridge, which is a Mid-Oceanic Ridge. This ridge is an underwater mountain range formed by plate tectonics, where new oceanic crust is created.
2. Indonesia is situated on the Pacific Ring of Fire and experiences numerous earthquakes due to the presence of a Subduction Zone. This is where one tectonic plate moves under another, causing significant seismic activity.
3. Nepal, located in the Himalayas, experiences seismic activity primarily due to Continental Collision. It lies at the boundary where the Indian plate collides with the Eurasian plate.
4. New Zealand lies along the boundary between the Pacific and Indo-Australian plates, where a Transform Fault exists. The Alpine Fault, in particular, is a transform fault that contributes to its seismicity.

Based on the matching above, the correct answer is: P-3, Q-1, R-4, S-2.

The tangential velocity ( ) of an object moving in a circular path is the distance traveled (circumference of the orbit, ) divided by the time taken ( , the orbital period).

$ \text{Variables} R 149 \times 10^6 \text{ km} T 365 \text{ days} \pi 3.14 \text{Required Unit Conversion} \mathbf{\text{km/hour}} T \text{2. Calculate the Tangential Velocity} \text{Calculation} \text{3. Rounding} $

To find the ratio of the surface gravity of the Earth to that of the Moon, we must use the formula for gravitational acceleration: , where is the mass and is the radius of the celestial body.

Step 1: Define the variables for Earth and Moon:

• Mass of Earth (where is the mass of the Moon)
• Radius of Earth (where is the radius of the Moon)

Step 2: Calculate for Earth and Moon:

• Earth’s surface gravity:
• Moon’s surface gravity:

Step 3: Determine the ratio of to :

The surface gravity of the Earth is 5 times that of the Moon.

Given:
Magnitude of first earthquake:
Amplitude at station:
Amplitude of second earthquake:
We need .
Step 1 — Use Richter magnitude formula:
where is a reference amplitude (same for both, so it cancels in difference). Difference in magnitude:
Step 2 — Plug in values:
Answer (rounded to two decimals):

The most abundant elements in the solar system, according to astronomical observations, are hydrogen (H), helium (He), oxygen (O), and iron (Fe). Hydrogen and helium are by far the most abundant elements, followed by oxygen and then iron.

Therefore, the correct order of abundance is H > He > O >Fe

The Benioff-Wadati zone refers to a subduction zone where an oceanic plate is being forced under a continental plate or another oceanic plate. Earthquakes within this zone occur due to the movement of the subducting plate, which is characteristic of the subduction zone setting.