Historical Data

The table below  lists the observed readings from each type of monitoring instrument used in Eruption! during a previous period of volcanic unrest.  Also listed is whether or not the volcano remained safe (dormant) over the subsequent 12 hour period.  Just looking at the table you can see that volcanoes tend to remain dormant when the readings are low.  But the correlation is not perfect; low readings do not always correspond with dormancy and sometimes the volcano remains dormant even when some of the readings are high.  That’s why volcanologists consider more than one than one type of data; the probability that a volcano will remain safe is greater if multiple types of data all indicate the potential for an eruption is low.

 

Time

Number of Earthquakes

CoSpec Reading (tons/day)

Change in Geodimeter Distance (mm)

Dormant?

10/20/86 12:00 PM

20

25

0

No

10/21/86 12:00 AM

18

36

0

Yes

10/21/86 12:00 PM

14

178

2

Yes

10/22/86 12:00 AM

27

493

5

No

10/22/86 12:00 PM

38

563

10

No

10/23/86 12:00 AM

38

605

10

No

10/23/86 12:00 PM

5

2

0

Yes

10/24/86 12:00 AM

48

913

4

No

10/24/86 12:00 PM

47

898

3

No

10/25/86 12:00 AM

25

334

5

Yes

10/25/86 12:00 PM

28

209

1

No

10/26/86 12:00 AM

8

136

0

Yes

10/26/86 12:00 PM

27

240

3

Yes

10/27/86 12:00 AM

6

2

0

Yes

10/27/86 12:00 PM

35

383

1

Yes

10/28/86 12:00 AM

9

107

0

Yes

10/28/86 12:00 PM

18

426

5

Yes

10/29/86 12:00 AM

42

703

10

Yes

10/29/86 12:00 PM

47

880

7

Yes

10/30/86 12:00 AM

9

23

0

Yes

10/30/86 12:00 PM

5

5

0

Yes

10/31/86 12:00 AM

3

0

0

Yes

10/31/86 12:00 PM

28

413

1

No

11/1/86 12:00 AM

2

5

0

Yes

11/1/86 12:00 PM

10

9

2

No

11/2/86 12:00 AM

13

13

4

No

11/2/86 12:00 PM

21

399

2

Yes

11/3/86 12:00 AM

22

443

1

Yes

11/3/86 12:00 PM

23

440

0

Yes

11/4/86 12:00 AM

20

236

0

Yes

11/4/86 12:00 PM

31

342

7

No

11/5/86 12:00 AM

33

488

4

Yes

11/5/86 12:00 PM

25

309

1

No

11/6/86 12:00 AM

24

306

0

No

11/6/86 12:00 PM

9

19

0

Yes

11/7/86 12:00 AM

7

7

0

Yes

11/7/86 12:00 PM

28

384

9

Yes

11/8/86 12:00 AM

32

496

1

No

11/8/86 12:00 PM

28

525

2

Yes

11/9/86 12:00 AM

16

405

3

Yes

11/9/86 12:00 PM

36

422

0

Yes

11/10/86 12:00 AM

36

495

2

No

11/10/86 12:00 PM

34

423

8

No

11/11/86 12:00 AM

47

743

3

No

11/11/86 12:00 PM

40

553

0

Yes

11/12/86 12:00 AM

4

0

0

Yes

11/12/86 12:00 PM

15

79

0

Yes

11/13/86 12:00 AM

5

105

4

Yes

11/13/86 12:00 PM

23

437

3

Yes

11/14/86 12:00 AM

24

460

2

Yes

A project funded by the U.S. National Science Foundation Human and Social Dynamics Program