A Geographer's Notebook: the world's biggest holes

What drove men to drill a hole into the earth’s crust, and what lies beneath the surface

Top 10 Amazing Holes In The Earth - Listverse

Who is drilling a hole more than 30,000 feet deep in the Earth's crust, and why? •

At the Edge of a Warming World

WWI Training Tunnels Discovered in England

The deepest hole we have ever dug

China is drilling some of the world's deepest holes in hunt for natural resources

Field notes, a historical perspective — Exploring Overland

Funny Gift Notebook for Geography Profess, BOOKS, JB 9781794084933

Ask Smithsonian: What's the Deepest Hole Ever Dug?, At the Smithsonian

Ask Smithsonian: What's the Deepest Hole Ever Dug?, At the Smithsonian

Greenland Is Melting

What's the deepest hole anyone has ever dug?

The Travels of Marco Polo — Volume 1, by Marco Polo and Rustichello of Pisa— A Project Gutenberg eBook

Geography Alive! Regions and People SE and ISN Sample (Unit 1 nad Unit 7) by Teachers' Curriculum Institute (TCI) - Issuu