Nov 3, 2002 Mw 7.9 Dec. 23, 1995 Shishaldin volcano sends ash N Denali earthquak

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Nov 3, 2002 Mw 7.9 Dec. 23, 1995 Shishaldin volcano sends ash N Denali earthquake March 11, 2011: Mw 9 Sept 15, 1994 Huge eruption of Tohoku earthquake, Kluchevshoi volcano. Ash cloud extends 565 km SE and nuclear over 10 km high Jan, 17, 1994: Mw 6.7 Northridge earthquake damages 100,000 buildings crisis; >18,000 dead or missing Jan. 17, 1995: Mw 6.9 72 deaths Kobe, Japan earthquake 5502 people killed Juan de Fuca Ridge June 3, 1991 Unzen, Japan volcanic eruption kifls 43 Emperor Searmount red) and chain June 28, Mw 7.3 Landers eart 3 geologists -42 My chain Kilauea Volcano erupts continuously since 1991 June 12, 1991: Mt. Pinatubo, Philippines eruption kills 722 people; volcanic ash cloud extensive (striped) Kauai 54 Myr AWAVIAN Ni'hau 3.4 Myr o'ahu IS LANDS 1.9 Mvz Moloka'i Maui CHAIN Lanai 08 Myr Mauna Kea olcano PACIFIC OCEA N 4 Myr Hawai'i Kilauea Volcano Volcanic peaks are red on map. Mauna Loa Volcano Lo'ihi .o Mr Seamount 0 -30 60 90 120-150 km Figure 2.13 Trail of the Hawaian hotspot. Top map shows the northern Pacific Ocean, adjacent landmasses, some notable geologic disasters, and the Hawaiian Islands and Emperor Seamount ChainsLower map shows details of the eastern Hawalian Islands Chain, including locations of major volcanoes. Myr means "million years".

Explanation / Answer

2. The rate of motion of pacific plate relative to hawaiian hotspot during 65 to 42 myr can be calculated as,

The lentgh of Emperor seamount chain =370 kms ( from map according to given scale)= 370×10^5 cms (as 1km=10^5cms)

The time duration of formation= 65-42=23 myr=23×10^6

years

Therefore, rate of plate motion = lentgh of seamount chain formed÷ time of formation=370×10^5÷23×10^6=1.61 cm/yr

The plate was moving slightly north west relative to the hotspot.

3. From 5.1 to 0.8 myr , the distance travelled by pacific plate relative to the hotspot = distance between kaua'i and maui= 340 kms=340×10^5cms

Time duration=5.1-0.8 myr=4.3myr=4.3×10^6yrs

Hence, the rate of plate motion during this period relative to hotspot= 340×10^5÷4.3×10^6=7.91 cm/yr

4. Rate of pacific plate motion relative to hotsopt between Lo'ihi and maui

Distance= 225 kms=225×10^5cms

Time =0.8-0.0=0.8 myr=0.8×10^6yr

Hence, rate of motion=225×10^5÷0.8×10^6=28.12 cm/yr

In all three questions above distancea are measured on scale of the map.

6. The pacific plate was moving north during 70 to 42 myrs but but later it moved west for upto 3.4 myr. Now it is moving north west relative to Hawaiian hotspot.

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