The Big Island has a lot of raw earth, literally raw, as in lava. It is a growing island, getting just a bit bigger every day as lava deposits and increases the size of the island.
The first stop on this itinerary is the Volcanoes National Park. This stop will be about 1-8 hours depending on how much hiking and exploring you hope to do. This is a large park with lots to see: steam vents, craters, lava trees, lava tubes, NeNe and other wildlife and flora. I suggest you check out the website for more information. The fee is $10 a vehicle including all it’s inhabitants or 5$ a person if walking or biking in. That fee allows entrance for 7 days. The site has some suggested itineraries based on how much time you have. I suggest you go to the visitor’s center and Jaggar museum (which btw, is a good place to see the new vent). Additionally, least do a short hike to see the Thurston Lava tube and if you have a bit of time take a longer hike there are some great day hikes around crater rims and through fascinating forests. If you are backcountry hiker, they’ve got those too (just give yourself a few more days and equipment).
The second stop on this itinerary is a lava flow. Nature is capricious. You never know if there will be a flow or not, or how easy it will be to see it. But the best place to to go to find out is probably either the USGS Volcano Observatory or Go Hawaii’s update. These will give you a good idea as to where to view lava flows. There is always a helicopter ride. They are not cheap, 150-200 per person, but spectacular. There are several companies that have tours out of Hilo. Since we haven’t yet availed ourselves of a tour, we suggest you try out Yelp or maybe TripAdvisor to get a rating on a good one. There are hiking tours as well, check this photo-gallery of one such tour.
The third stop on this itinerary is Lava Tree State Monument. This small park only takes an hour perhaps to see, but it well work it. Lava from a past flow was wicked up the moist trees and then cooled, killing the tree but leaving eery lava casts of the tree. You can see it on the way to a tour or Volcanoes National Park.