just the tip of the iceberg

just the tip of the iceberg

Only a small, often unrepresentative portion of something much larger or more complex that cannot yet be seen or understood. If Congress doesn't vote to extend the debt limit, a government shutdown will be just the tip of the iceberg. The flooding is bad, but we're dealing with just the tip of the iceberg: a huge spate of environmental disasters are on the horizon because of climate change.See also: iceberg, just, of, tip