When a volcano erupts, how much time do residents have to evacuate? That depends. Lava flows downhill and travels faster over steep ground. In the early 1990s, residents of Kalapana, a town in the southeastern Puna region, had days or even weeks to prepare for a lava flow that eventually covered the town. By contrast, a 1950 lava flow down the western flank of Mauna Loa reached the sea in about four hours. Although scientists monitor ground movement on the island continuously, there is no way to know how much advance notice residents living downhill of an eruption will receive.
In this lesson, you'll begin to explore the relationships among lava flow zones, emergency shelters, and population. By the end, you'll be ready to ask some questions that you'll answer in the remaining lessons.
Open the map and explore the data
- Go to the ArcGIS Online group, Analyze Volcano Shelter Access in Hawaii. When prompted, sign in to your
ArcGIS organizational account.
If you don't have an organizational account, you can sign up for an ArcGIS free trial.
- Click the Content tab, then click the thumbnail of the Shelter Access Analysis map to open it.
- On the details page, click Open in Map Viewer.
The map opens to the island of Hawaii.
As shown in the legend, the island is divided into nine categories of lava flow risk, from extremely high hazard to extremely low hazard. Under the partially transparent zones, census blocks symbolize population density (people per square mile) in shades of gray. The map also shows the locations of volcanoes and emergency shelters.
- On the map, click a volcano to see its pop-up.
You see the volcano's name, elevation, type, and date of last eruption.
In this example, the pop-up title bar shows "1 of 4". When you open a pop-up, you also access pop-ups for other features at or near the same location. (These may be in the same layer or different layers.) Click the white arrow in the title bar to see the other pop-ups.
- Open the pop-ups for the other volcanoes.
Hualalai, Mauna Loa, and Kilauea are active. Mauna Kea is extinct. Loihi is also active, but since it’s undersea, it’s not a factor in this analysis.
- On the ribbon above the map, click the Bookmarks button and choose Kona.
- Open the pop-up for an emergency shelter.
Almost all the emergency shelters on the island are schools.
- Close the pop-up.
- On the ribbon above the map, click the Bookmarks button and choose Hilo – Puna.
The map zooms to the island’s east coast. Hilo is the island’s largest town, and most of the population lives in or near it. At this scale, the census blocks are easier to see under the hazard zone.
- Click a hazard zone to see its pop-up. (If a pop-up for a different layer appears, use the arrow in the pop-up title bar.)
Hilo lies in a high hazard zone, as do the populated places to the south.
- Open pop-ups for the other lava flow hazard zones in the area.
- When you're finished, click the Bookmarks button and choose Kona.
- Open the lava flow hazard zone pop-ups in this area.
The west coast is the other main population center on the island. Most of the people here live along the Kohala Coast, a medium-high hazard zone. Many also live in the high-hazard Mauna Loa Northwest Slope zone to the south.
- Use bookmarks to explore the other parts of the island. When you're finished, zoom to the Hawaii Island bookmark.
As you start to work with analysis tools in the next lesson, you'll need to have your own copy of the map.
- On the ribbon, click the Save button and choose Save As.
- In the Save Map window, change the title to Shelter Access Analysis.
- Click Save Map.
The map is saved to your content page in the organization.
Many people, on different parts of the island, live in high-hazard lava flow zones. Usually, there are a good number of emergency shelters in these areas. But how accessible are these shelters? And how should accessibility be measured? Which high-risk parts of the island may need additional shelters? In the next lesson, you'll use analysis tools to evaluate shelter access for the brave mortals who put themselves in Pele's way.