Interior structure of the earth

Correct answer: B. Indirect source

Seismic waves give indirect information about inner layers. Exam tip: remember seismic waves as the most important indirect source.

Correct answer: A. Upper crust

Mining mainly gives information limited to the upper crust. Exam tip: remember the limitation of direct sources too.

Correct answer: A. They indicate Earth like building material

Meteorites give clues about Earths formation and composition. Exam tip: keep meteorites as indirect clues.

Correct answer: A. Crust mantle core

On chemical basis the major layers are crust mantle and core. Exam tip: connect chemical division with three major layers.

Correct answer: A. Plastic and partly molten behavior

Asthenosphere shows plastic and partly molten behavior. Exam tip: connect weak zone with asthenosphere.

Correct answer: B. Liquid outer core

Movement of metallic material in the liquid outer core is linked with the magnetic field. Exam tip: connect magnetic field with outer core.

Correct answer: A. Lithospheric plates

Mantle convection currents help the movement of plates. Exam tip: connect convection with plate tectonics.

Correct answer: B. Mantle

The mantle occupies a large part of Earths volume. Exam tip: remember mantle as the thickest major layer.

Correct answer: A. It is the thinnest major layer of Earth

The crust is the thinnest major layer of Earth. Exam tip: remember crust as the thin outer layer.

Correct answer: B. Oceanic crust

Basalt is a dark, fine-grained volcanic rock that is especially common in oceanic crust. Oceanic crust forms mainly from magma that rises at mid-oceanic ridges, cools, and solidifies under the sea. Its composition is therefore largely basaltic. Continental crust is generally richer in lighter rocks such as granite, while the inner and outer cores are made mainly of metallic materials, not ordinary basaltic rocks.

The key comparison is between continental and oceanic crust. If a question asks for the layer dominated by basaltic rocks, choose oceanic crust because new seafloor is produced from basaltic lava. The inner core is solid and the outer core is liquid, both consisting chiefly of iron and nickel under extreme pressure and temperature. Thus option B, oceanic crust, correctly matches the rock type described.

Correct answer: A. Continental crust

Continental crust is linked with granitic rocks. Exam tip: connect granite with continental crust.

Correct answer: B. Boundary or discontinuity of layers

Change in wave velocity indicates boundary between layers. Exam tip: remember discontinuity through velocity change.

Correct answer: B. Change boundary between two internal layers

The direct answer is B: a discontinuity is a boundary where the properties of two internal layers change. In Earth science, a layer may change in composition, density, state or the speed of seismic waves. Reasoning: Earth has internal layers; the material in one layer is not always like the material in the next; the transition zone is called a discontinuity; seismic waves may change speed or direction there. A is wrong because a forest is a surface feature, not an internal boundary. B is correct. C is wrong because ocean-water colour has nothing to do with Earth’s internal layering. D is wrong because air pressure is an atmospheric idea, not the meaning of a geological discontinuity. Examples include the Moho and core-mantle boundary, but the simple exam meaning is a change boundary between layers. Memory cue: discontinuity means a break or change in continuity.

Correct answer: A. Density increases

Heavier materials are more abundant toward the center so density increases. Exam tip: keep density and depth together.

Correct answer: A. Crust mantle core

From surface to center the correct order is crust mantle and core. Exam tip: identify this order in diagrams.

Correct answer: C. Core

The core is Earth’s innermost layer and is considered its central part. It is composed mainly of iron and nickel. The mantle lies above the core, while the crust is the outermost layer. Exam tip: remember the order from outside to inside—crust, mantle, core.

Correct answer: A. Oxygen and silicon

Oxygen and silicon are major elements in the crust. Exam tip: remember these two first in crust composition.

Correct answer: A. Thickness composition and density

The two crust types differ in thickness composition and density. Exam tip: remember the comparison of continental and oceanic crust.

Correct answer: B. Oceanic crust

Oceanic crust is found beneath the ocean floor. Exam tip: connect ocean floor with oceanic crust.

Correct answer: B. Thicker

The crust is generally thicker beneath mountain regions. Exam tip: connect mountains with thicker crust.

Correct answer: A. Mantle

The mantle is considered to have hot dense silicate rocks. Exam tip: connect mantle with rocky silicate layer.

Correct answer: A. Outer core — liquid

The outer core consists mainly of molten iron and nickel, so it is liquid in physical state. The inner core is solid because of immense pressure, not liquid. The crust is solid, and the mantle is not completely gaseous; it is largely solid but flows very slowly over long periods. Exam tip: remember the pair outer core—liquid and inner core—solid.

Correct answer: A. It shows heavier materials are more common at depth

Density helps understand distribution of materials inside Earth. Exam tip: connect heavy materials with deep layers.

Correct answer: A. Crust and core

The outermost major part is crust and the innermost part is core. Exam tip: remember outermost crust and innermost core directly.

Correct answer: D. Density differentiation

Heavy materials moved toward the center because of higher density. Exam tip: connect iron nickel core with density differentiation.