Sources of information

Crust sample is limited and seismic clues are needed for deep parts. Exam tip: identify the scope of a source.

Meteorites do not come directly from Earth's interior. Exam tip: connect them with comparison of early materials.

Volcanic material comes from inside but does not represent every deep layer. Exam tip: write both use and limitation.

Both are indirect clues so verification is needed. Exam tip: write combined evidence for conflicting clues.

Radioactive decay can produce heat and mine temperature gives a limited clue. Exam tip: separate cause and observation.

Local sample is limited and global seismic data gives depth clues. Exam tip: understand source scope.

The direct answer is A, when the anomaly only indicates mass and density. A gravity anomaly is an indirect geophysical clue. Gravity depends mainly on how mass is distributed, and density is an important part of that distribution. Different rocks or underground structures can produce similar gravity effects, so the observation alone does not identify a definite chemical composition. The reasoning is: measure a difference in gravitational attraction; infer a difference in underground mass or density; do not directly name the minerals or chemical elements; use samples or laboratory tests for stronger chemical evidence. Option A is correct because it states the limitation of the observation. Option B, laboratory testing of a rock, gives direct evidence from the material itself, so it is not the problematic situation. Option C, an available mineral sample, can be chemically examined and is more direct. Option D, a drilling core, physically brings underground material for analysis and is also more direct. The exam cue is: geophysical anomalies suggest structure or density; laboratory samples reveal composition more directly.

Different sources reveal different parts of the Earth's interior. Seafloor rocks provide evidence about oceanic crust and the materials found near the surface. Seismic waves travel through the Earth and their speed, direction, reflection, refraction, and shadow zones help scientists infer the nature and boundaries of deep layers. Mining samples are obtained directly, but they usually represent only a limited part of the shallow crust because mines cannot reach the deepest regions.

Option D is the incorrect match. A rain gauge measures rainfall, which is a surface weather observation; it does not directly reveal the state or physical condition of the outer core. The other matches are reasonable: ocean-floor rocks relate to oceanic crust, seismic waves provide clues about deep layers, and mining samples offer limited crustal evidence. The question tests whether the source is actually capable of supplying information about the stated part of Earth.

The direct answer is A: lava is not a direct sample of the whole core. Lava is molten rock that reaches the surface during a volcanic eruption. It comes mainly from magma generated in particular parts of the crust or upper mantle, so it can provide clues about some interior materials, but it cannot represent every layer of Earth or the entire core. Therefore, the safe reasoning is: lava is volcanic material; volcanic material may reflect some underground composition; the core is much deeper and has different conditions; so claiming that lava is a sample of the whole core is an overextended conclusion. Option A is wrong because it makes a claim far beyond the evidence. Option B is correct as a description because lava is surface material produced by volcanic activity. Option C is also scientifically reasonable because lava can give information about some internal rocks and processes. Option D is important because every source of information has limits, and those limits must be recognised. Memory cue: useful evidence is not the same as complete evidence.

Rock analysis tells composition of real material. Exam tip: choose sample analysis in chemical questions.

The direct answer is A: it is wrong to decide the state of deep material from a surface sample when temperature and pressure are different at depth. A surface rock can show its mineral composition, but it does not automatically show the physical condition of material far below Earth’s surface. The reasoning is: depth causes pressure to rise and temperature generally to rise; these conditions can change melting, density and the state of rocks; therefore a surface sample alone may mislead us about deep material. Option A correctly identifies this limitation. Option B is not wrong because a local surface rock can be identified by examination. Option C is not wrong because mineral testing is a suitable use of a sample. Option D is not wrong because surface samples and other evidence can help study crustal composition, although they may not reveal the whole interior. Memory cue: a surface sample tells us about the surface, not automatically about deep temperature-pressure conditions.

Direct and indirect sources give information at different levels. Exam tip: write comparative and balanced answer.

Indirect clues are verified by comparison with other evidence. Exam tip: use cautious language.

Gravity anomaly relates to difference in mass and density. Exam tip: do not treat it as chemical sample.

Drilling gives real sample and temperature data but depth is limited. Exam tip: write use and limitation together.

Matching clues from many stations increase reliability. Exam tip: write multi-station evidence.

Magnetic field gives indirect clue of possible metallic materials. Exam tip: do not write it as direct sample.

The direct answer is A, when the sample is local and from shallow depth. A direct sample gives real information about the place and depth from which it was collected, but it cannot automatically represent the entire Earth. Step by step: identify the sample’s source; note that it comes from a limited and shallow area; compare that limited evidence with the much deeper and wider interior; use it carefully alongside seismic waves, gravity, magnetic evidence and other observations. Option A is correct because a local shallow sample has a narrow scope, so its conclusion must be cautiously applied to a whole-Earth model. Option B is not a realistic ordinary direct sample: no routine sample comes from the whole core, and even such a claim would need evidence. Option C, weather, is not a direct rock sample of Earth’s interior. Option D, population, is a human statistic and cannot reveal interior composition. The key lesson is representative evidence: a small observation may be useful, but its conclusion must not be enlarged beyond its limits. Memory cue: local sample, limited conclusion.

Volcanic material and meteorite are both useful but different in nature. Exam tip: identify source origin.

Seismic waves give clues and help in deep information. Exam tip: write both use and limitation.

Expert answer includes role and limitation of source. Exam tip: keep conclusion evidence based.

Seismic waves show state and boundary while gravity and magnetism give supporting clues. Exam tip: use multi-source analysis.

Deep parts are hard to reach so seismic and other indirect sources are important. Exam tip: write problem and solution together.

Balanced study is based on combined analysis of many sources. Exam tip: write roles of both direct and indirect sources.

Drill core is direct but local while multi-station wave data indicates deep boundary. Exam tip: draw conclusion according to source scope.