Impacts of Climate Change on the Pacific Northwest

August 25, 2019

Geology Blog 2: Unveiling the landscapes of the Olympic Peninsula

This is the second blog by the geology group. The day we set off for the Olympic Natural Resource Center (ONRC), We felt a little bittersweet because we would say goodbye to Pack Forest but we would get to see the Olympic Peninsula!

After a 4 hour drive, we finally reached Ruby beach. From the parking lot, we followed the trail down to the beach along a winding and bumpy path and arrived at the beach with a lot of driftwood. Near the end of the trail, there was a large pool piled with rocks. Not far from the pool, was Ruby beach. We walked along the beach and found the sea cliff and sea stacks. The sea stacks were formed by the ocean waves, which made the variety of coastal landscape features. For example, with the waves impacting the rocks, erosion takes place. This erosion forms caves 1, holes, and arches 2. The continual current can cause the top of the arch to fall, leaving nothing but the sea stacks 3.

We were confused why the gravel that made up the beach, and the rock formations at Ruby beach were so different from what we are familiar with in China 4. We wondered how the steep cliffs and rock formations were formed.

Figure cations: 1: sea stacks (photo by: Jiangyi Zhang) 2: sea cliff, sea stacks, & gravel (photo by: Jiangyi Zhang) 3. Geological profile concept map 4. the sign about Tsunami

We figured out that the name of the rock outcrops along the coast of the Olympic Peninsula in Washington State are called Hoh rocks 5. Hoh rocks are not just from a single stratum, but a group of rocks that differ greatly in composition and geological age, many of which are combinations of siltstone, sandstone and gravel. The Hoh rocks originated from sediments in the deep-sea basin, which was formed by squeezing, accumulating and lifting because of crustal movement and plate uplift caused by collision between the Juan de Fuca and North American plates. As we know, earthquakes are caused by plate collisions, which can lead to tsunamis. This is the reason why there are signs identifying evacuation routes in case of tsunamis in coastal areas. We saw several of these signs from our bus.

When we arrived at the Hoh Temperate Rainforest in the Olympic National Park, we encountered a river with slow moving water, and a milky white color. Our guest speaker, Joseph Murray, identified the river as the Hoh River 6. The Hoh river is a river fed by glaciers from Mount Olympus, such as Hoh Glacier. The rocks on the mountain are grinded by glaciers into a fine glacier flour which turns the Hoh River a milky white color. The flat and broad river valley causes the glacier sediments to settle out and creates many gravels bars.

Hoh River photo by: Dayang Zhao

Hoh Glacier is the longest glacier 7 in the Olympic Mountains, with a length of 3.06 miles. However, the volume of Hoh Glacier has decreased by 16% from 1987 to 2009, and the coverage area has decreased by 20% from 1980 to 2009 8,9. This is not the only glacier to shrink. As the climate warms, the temperature rises the fastest at the higher latitudes and higher altitudes. The glaciers of the Olympic Mountains have shrunk from 45.9 in 1980, to 30.2 in 2009. The coverage area has been reduced by 15.7, nearly 34% 8,9.

Change in glacier extent on Mount Olympus from AD~1980 to present 8.

At present, global warming is a severe problem and it heavily impacts glaciers. Global warming has intensified the melting of glaciers which has resulted in sea-level rise and has affected human activities as well as ecosystems. Eight of the ten biggest cities in the world are located by the coast, such as Shanghai and New York. Those cities are home to a significant portion of the world’s population. An article from National Geographic used a model to estimate the sea-level rise if the ice sheet of Antarctica completely melted 10. It showed that the mean sea-level will rise would be 60 meters, and Nanjing would be flooded while Seattle wouldn’t be.

Estimated sea level in North America and China if Antarctica melted10.

To sum up, what we saw today was caused not only caused by the earth’s internal forces like plate movements, but also external forces like erosion. Climate change is a complicated issue, which impacts all systems and cycles on the planet. So, we should think more about the coupling mechanism of the atmosphere, hydrology, geosphere, biosphere in order to understand better the relationship between climate change and human activity.

Reference

  1. (https://en.wikipedia.org/wiki/Sea_cave)
  2. (https://www.touropia.com/sea-arches/)
  3. (https://en.wikipedia.org/wiki/Stack_(geology))
  4. (https://www.chinahighlights.com/travelguide/article/beautiful-islands.htm)
  5. (https://www.dnr.wa.gov/publications/ger_b66_geol_wa_coast.pdf)
  6. (https://en.wikipedia.org/wiki/Hoh_River)
  7. (https://en.wikipedia.org/wiki/Hoh_Glacier)
  8. RIEDEL, J., WILSON, S., BACCUS, W., LARRABEE, M., FUDGE, T., & FOUNTAIN, A. (2015). Glacier status and contribution to streamflow in the Olympic Mountains, Washington, USA. Journal of Glaciology, 61(225).
  9. Spicer RC (1986) Glaciers in the Olympic Mountains, Washington: present distribution and recent variations. (PhD thesis, University of Washington).
  10. https://www.nationalgeographic.com/magazine/2013/09/rising-seas-ice-melt-new-shoreline-maps/