We've learned about all the enormous time spans that describe the billions of years in Earth's history, but how did we arrive at these dates? How can we know the age of the Earth? Let's learn about some dating methods, starting with...

WS T/L POV View of Heads towards density of tree covered limestone islands, many other tourist boats in interconnecting channels / Ha Long Bay, Vietnam

Flora and Ritchie Roberts Reserve and Curl Curl, NSW, Australia from the air

WA View across rocky outcrops in Sahara desert, Hazy, Algeria, Africa

Limestone Outcrop, Addleborough

The highway in the karst landscape in guilin

Karst area of the sunset.

The highway in the karst landscape in guilin

Wadi Rum - a valley cut into the sandstone and granite rock in southern Jordan 60 km (37 mi) to the east of Aqaba; it is the largest wadi in Jordan

MS Grey seal (Halichoerus grypus) group sitting on seaweed covered rocky outcrop, resting, Norfolk, UK

WS Shot of School of sweepers swimming or drifting with surge around rocky outcrop covering with swaying seaweed / Matola, Maputo, Mozambique

MS Shot of Rocky outcrop covering with various seaweed swaying with surge / Matola, Maputo, Mozambique

WS AERIAL T/L View of Desert crags interrupt flat scrubby grasslands and sand and huge golden distance under soft blue sky and streaming white clouds / Windhoek, Namibia

Famous sandstone outcrops at Garden of the Gods, a Colorado Springs park. Canon 5dmII, 1080P HD, 30fps, Canon 5dmII, 1080P HD, 30fps, shutter speed 1/60 sec Camera pan/zoom

Cave entrance in rocky outcropping with caravan of camels below / men heaving large block of stone / VS camels being guided by owners inside cave past huge boulders and outside / workers loading heavy blocks of stone on backs of camels /...

two men on train sit at table and look out window / POV from back of train of Andes mountains as it moves up steep track / POV from back of train of snow covered tree barren Andes mountains as it moves up almost very steep track / POV...

Road through village with rocky backdrop, near Petra, Jordan

Karst area of the sunset.

Karst area of the sunset,Guilin,China

Karst area of the sunset.

Padern Castle - Aerial View - Languedoc-Roussillon, Aude, Arrondissement de Narbonne, France

Small islets lie within Kalaupapa National Park, a remote area including the north central coast of Molokai. The national park protects many threatened and endangered species endemic to the Hawaiian islands.

Aerial view of the granite Two Peaks East in the Eldorado National Forest.

Karst area of the sunset,Guilin,China