Lecture 5, 6, and 7 - Geologic Time, Yellowstone, and Hawaii Volcanos

Lecture 5, 6, and 7

how long ago was the first life on earth

550 ma (biological big bang, NOT humans yet)

list the eras of geologic time

[old] Paleozoic, Mesozoic (dinos), Cenozoic (ppl at end) [new]

if earths history put on a yr long scale, what would we see

First mineral early January, Biological Big Bang November, giant extinction early December, dinos early ish December, humans very end of December.

When and where did the Yellowstone hotspot begin

16ma in Oregon

how many caldera forming eruptions have occurred in present day yellowstone

3

How many hydrothermal features in Yellowstone

over 10,000

How many volcanos are on Hawai’i and which ones are in the national park?

5, Mauna Loa and Kilauea

What is Manau Loa’s elevation

13,679 at sea level or 32,000 from ocean floor

how tall were the lava fountains of Kilauea’s last eruptive phase in January 2026

1,500 ft tall

When did Mauna Loa last erupt?

2022

Which type of lava is rubbly vs smooth

A’a is rubbly, Pahoehoe is smooth

What is a Hotspot

A thermal upwelling of magma (mantle wells up → decomposes → melts → basalt) (crustal rock → melts → explosive Rhyolite). a hotspot happens when magma comes up in middle of plate. It stays in one spot, but the plate moves over it creating a trail of eruptions.

What is a caldera

volcanic feature that collapsed cuz of withdrawal of magma. 1km or more in width.

Explain Pyroclastic Density Currents (PDCs)

A caldera-forming eruption lets of a hot cloud of ash, rock, and gas - a PDC. PDCs deposit onto ground either welded (called Tuffs) or unwelded. Tuffs have no layers and are in big deposits. the most recent was lava creek 640ka.

When was the most recent caldera forming eruption

lava creek, 640ka

what is huckleberry ridge

Biggest Yellowstone eruption, 2.1ma, 185m thick tuff.

what formed the trenches and canyons of yellowstone

giant ice cap melt 15ka

What makes a hydrothermal feature

rain goes down, heat+fluid+rock mix under lightly molten magma chamber 5km below yellowstone, then come up as a hydrothermal feature

Mammoth Hot springs

Cools into shelves of travertine

Grand Prismatic Spring

Rim has thermophilic microbial organisms making it a pretty color

What is VEI scale

Volcanic Explosivity Index (VEI), a logarithmic scale from 0 to 8. the Lava Creek and Huckleberry Ridge eruptions were VEI 8 ("mega-colossal"), which classifies them as "supervolcanoes" (defined as ejecting over 1000 km³ of material)

Explain how Old Faithful works

Water in rocks is hot and has a lot of pressure. It flashes into steam and erupts.

What are mudpots and fumarols

Mudpots are water and clay, fumarols are steam and gas (from the degassing of magma chamber below)

How many species of wildlife are in yellowstone and what are the main ones

67; Bison, elk, Grizzley bears, and wolves

When was Yellowstone Est.

1872

When was Hawaiʻi Volcanoes National Park Est.

1916

What type of volcanos are on Hawai’i?

5 sheild volcanos - Tall and wide with low elevation gradients at areas with sustained production and low viscosity mafic magma.

List the 5 volcanos, their activity status, and when they last erupted.

Kilauea - active, Dec 23 2026

Mauna Loa - Quiescent, 2022

Hualalai - Quiescent, 1801

Mauna Kea - Dormant, 2460 BCE

Kohala - Extinct, last 60,000 yrs.

What are lava tubes

Lava tubes form when magma flows beneath an insulated crust; when the lava drains away, it leaves behind hollow cave systems.

how long ago did the Hawaiian-Emperor Seamount Chain start

The Hawaiian-Emperor Seamount Chain stretches back at least 64.7 million years to the Aleutian Trench

What are Xenoliths

Erupting basalts sometimes carry "xenoliths"—solid chunks of green olivine eroded from the Earth's mantle—giving geologists a rare window into Earth's deep interior

What are Tumuli

mounds formed when the brittle crust of a pahoehoe flow is inflated upward by the pressure of the flowing lava beneath it

What are lavacicles

drip-like pendants hanging from the ceiling of lava tubes