The ocean floor has ridges, mountains, canyons and trenches. Challenger Deep in the Mariana Trench is the deepest known ocean location, not the name of the entire trench. We will use rounded values: about 10.9 km below sea level there and about 8.85 km above sea level for Everest. Safety: No diving, climbing or water experiment. Stop: Stop after the paper comparison. Do not model depth in baths, pools or containers.

Materials: Paper; Pencil; Optional ruler 1. Draw a horizontal sea-level line and a separate profile below it with a shallow shelf, a slope, a flat deep plain, a raised ridge and a narrow deep trench. Label each feature. The profile is illustrative, not a measured cross-section of one real route. 2. Beside it, draw a comparison axis with 0 at sea level, marks to 9 km above and 11 km below. Use equal spaces. If a ruler is unavailable, count matching drawn spaces rather than claiming a precise physical scale. 3. Mark Everest at about +8.85 km and Challenger Deep at about −10.9 km. Explain that height and depth are measured from the same sea-level reference in this comparison. Mark the trench as part of the western Pacific. 4. Imagine moving Everest so its base rests at Challenger Deep. Compare the two lengths: would its summit reach the surface? Write the answer and say why this is only a size comparison, not a possible mountain-moving experiment. Done: Complete a labelled terrain profile and equal-interval comparison showing that the depth exceeds the mountain height. Proof: Keep both drawings and the underwater-summit answer. Note help placing decimal positions or setting intervals. Stop: Stop after the paper comparison. Do not model depth in baths, pools or containers.