Hawaii (The Big Island) is definitely that - big. From massive craters to lava flowing into the ocean to the tallest mountain in the island chain, it is hard to comprehend.
The first day starts near the shore looking across a vast lava field. In the distance the steam from lava pouring into the ocean can be seen.
After some driving up a mountain, you enter the Volcanoes National Park. At the park headquarters there are many great hikes to experience first hand the power of nature. The Crater Rim Trail (#6) wonders past cracks in the earth emitting sulfur smelling steam, down through a forest hidden path and ultimately to the edge of the Kīlauea crator floor (with a warning sign not to proceed further). Going to the edge of the sign, my eyes started watering and my throat stung. A fast retreat and back along the trail as it climbed back up and followed along the rim of the crater.
The Kīlauea Iki Trail (#32) actually crosses a (safe when I was on it) crater floor giving an entirely different perspective.
A great way to round out the hiking in this area is to walk through the Thurston Lava Tube (#79). After that subterranean adventure, it is an easy walk back to the visitor's center, partially following a closed off road. At one point clouds hovered over the main crater. (#109) The steam and gas from the main vent hole (with a live lava lake in its bottom) was dramatically visible through the light rain and spots of sunlight peaking through.
From there a drive down the Chain of Craters Road follows the history of lava flows towards the ocean. The time I was on the road it was blocked at the end due to an active flow. But along the way, deep craters, extensive lava fields, and eventually, where the landscape dropped towards the ocean, the sunset against the steaming flows.