Final answer:
To build a glacier, winter snowfall must exceed summer melting, allowing snow to accumulate and form ice that moves under its own weight. A glacier on the land would cause a greater increase in the lake's water level when melted compared to an iceberg already floating on the lake.
Step-by-step explanation:
The condition most necessary to build a glacier is that the winter snowfall must exceed summer melting. This allows snow to accumulate over time and compress into ice, forming a glacier. If snowfall does not significantly exceed the melt, the snow will simply melt in the warmer months and a glacier cannot form. Glaciers move under their own weight and can be detected by the presence of crevasses. Understanding the dynamics of glaciers is crucial, especially in light of rising global temperatures and their potential impact on glacier retreat. For instance, in Glacier National Park, USGS scientists have studied and defined glaciers based on size; glaciers must cover at least 0.1 km2 to be classified as such. As the climate changes, ice masses, including glaciers, are subjected to melting which can influence sea levels and freshwater supplies.
When considering an iceberg in a lake and a glacier on land, it's the glacier on land that would cause a greater increase in the lake water level when melted. This is because the iceberg is already floating on the water, and by Archimedes' Principle, it has already displaced an amount of water equal to its weight. Melting would not change the water level significantly. The glacier on land, however, when melted, will contribute additional water to the lake that was not previously there, thus raising the lake's water level.