Most Well-Studied Geology on Earth?

The question went out to several dozen Geologists:

What is the most well-studied geology on Earth?

The question casts a wide net and I was hoping to see some creative answers. I was not disappointed. From individual formations (Old Red Sandstone) to global phenomena (MORBs) to celestial bodies (The Moon), the responses confirm the fact that the modern Geologist is as well-traveled as ever. While the top vote getters do show a bias for the US Cordillera, its an easy thing to forgive. The rocks, the mountains, and the beer are better here. In the end, there was a tie for the top spot:

#3 - US Mines & Oil Basins

#2 - Yellowstone National Park / Yellowstone Hot Spot

#1 - The Alps

#1 - San Andreas Fault

Below is a summary of the remaining responses organized into award categories.

"Big Picture Thinker" Award Winners Mid-Ocean Ridge Basalts (MORB) Cretaceous-Tertiary Boundary

Sea Ice

Human-impacted Environment

"It Would Be More Interesting If It Had Actually Been Cheese" Award Winner

The Moon

"SoCal Nerds Win More NSF Dollars" Award Winner

Southern California - All of it

"Rocky Mountain Water & Colorado Plateau Sediment" Award Winners

Grand Canyon

Heart Mountain Detachment, WY

"We Have to Map This Again?" Award Winners The State of Kentucky

Cascade Volcanoes, WA-OR-CA

Scotland

Puget Lowland, WA

Willamette Valley, OR

Japan

Butte Copper Mines, MT

"Why Do Euros Wear Spandex to the Outcrop?" Award Winners

Great Britain (Continuously remapped since 1815)

European stratigraphic units i.e., Old Red Sandstone, Permian Zechstein & Paris Basin strata Siccar Point, Berwickshire, Scotland (Hutton's Unconformity)

Burgess Shale, BC (Canada was a subject of England, not France)

"The EPA Guy Hates Us" Award Winners

Appalachian Coal Basins

Gulf of Mexico/Gulf Coast, USA

Texas-Oklahoma Petroleum Basins

Hanford Nuclear Site, WA

Yucca Mountain/Nevada Test Site

Mines (The most detail per square mile)

My mapping in the Picuris Range, NM as a student on University of Wyoming's field camp back in 1996. I subsequently attended UWyo and TA'd the summer field course for 3 years and the fall course twice.