Per 
Image taken by agent ██ in the first expedition.
Item #: SCP-4921
Object Class: Safe
Special Containment Procedures: Because of its nature, SCP-4921 must be contained in place. Islands that contain SCP-4921 must be isolated from the outside within a radius of 150km.
Description: SCP-4921 is a combination of electromagnetic rays that creates a 100m in height wall that surrounds 4 islands. SCP-4921 only appears once a year and will shrinks, leaving behind an area affected by electromagnetic rays. All objects in its sphere of influence won't be affected, except living organisms. All living organisms except trees if in its sphere of influence will be corroded, approximately 0.4% body per second.
SCP-4921 will undergo 3 narrowing processes, each time is 5 minutes apart and takes 2 minutes to complete a process:
- First time: Start 5 minutes after appearing, narrows to 7km.
- Second time: Start 5 minutes upon completing the first process, narrows to 2km.
- Third time: Start 5 minutes upon completing the second process, narrows to 2km.
The islands that contain SCP-4921 include:
- SCP-4921-A
Area: East of Russia
Coordinates: [DATA EXPUNGED]
- SCP-4921-B
Area: West of North America
Coordinates: [DATA EXPUNGED]
- SCP-4921-C
Area: North of Asia
Coordinates: [DATA EXPUNGED]
- SCP-4921-D
Area: South of the East Sea
Coordinates: [DATA EXPUNGED]
All of these islands are 6km wide, and has been abandoned since the SCP-4921 first appeared in 19██. [DATA EXPUNGED]
Addendum 4921-A:
The expeditions:
